NRLF 


B   M   5E14   271 


LIBRARY 


UNIVERSITY  OF  CALIFORNIA. 


Class 


PRINCIPLE  OF  HOT  WATER  HEATING  ILLUSTRATED  BY  TRANSVERSE  SECTIONAL 
VIEW  SHOWING  BOILER,  RADIATOR  AND  EXPANSION  TANK. 

American  Radiator  Company. 


Heating 
and  Ventilation 


A  Working  Manual  of 

APPROVED   PRACTICE  IN   THE   HEATING  AND  VENTILATING  OF  DWELLING- 
HOUSES  AND   OTHER    BUILDINGS,   WITH    COMPLETE   PRACTICAL  IN- 
STRUCTION IN  THE  MECHANICAL  DETAILS,   OPERATION,    AND 
CARE  OF  MODERN  HEATING  AND  VENTILATING  PLANTS 


By  CHARLES  L.  HUBBARD,  S.  B.,  M.  E. 

Consulting  Engineer  on  Heating,  Ventilating,  Lighting,  and  Power 


ILLUSTRATED 


OF  THE 

UNIVERSITY 

OF 


CHICAGO 
AMERICAN  SCHOOL  OF  CORRESPONDENCE 

1909 


GENERAL 


COPYRIGHT  1908  BY 
AMERICAN  SCHOOI,  OF  CORRESPONDENCE 

Entered  at  Stationers'  Hall,  L,ondon 
All  Rights  Reserved 


Foreword 


recent  years,  such  marvelous  advances  have  been 
made  in  the  engineering  and  scientific  fields,  and 
so  rapid  has  been  the  evolution  of  mechanical  and 
constructive  processes  and  methods,  that  a  distinct 
need  has  been  created  for  a  series  of  practical 
working  guides,  of  convenient  size  and  low  cost,  embodying  the 
accumulated  results  of  experience  and  the  most  approved  modern 
practice  along  a  great  variety  of  lines.  To  fill  this  acknowledged 
need,  is  the  special  purpose  of  the  series  of  handbooks  to  which 
this  volume  belongs. 

C,  In  the  preparation  of  this  series,  it  has  been  the  aim  of  the  pub- 
lishers to  lay  special  stress  on  the  practical  side  of  each  subject, 
as  distinguished  from  mere  theoretical  or  academic  discussion. 
Each  volume  is  written  by  a  well-known  expert  of  acknowledged 
authority  in  his  special  line,  and  is  based  on  a  most  careful  study 
of  practical  needs  and  up-to-date  methods  as  developed  under  the 
conditions  of  actual  practice  in  the  field,  the  shop,  the  mill,  the 
power  house,  the  drafting  room,  the  engine  room,  etc. 

C,  These  volumes  are  especially  adapted  for  purposes  of  self- 
instruction  and  home  study.  The  utmost  care  has  been  used  to 
bring  the  treatment  of  each  subject  within  the  range  of  the  com- 


179734 


mon  understanding,  so  that  the  work  will  appeal  not  only  to  the 
technically  trained  expert,  but  also  to  the  beginner  and  the  self- 
taught  practical  man  who  wishes  to  keep  abreast  of  modern 
progress.  The  language  is  simple  and  clear;  heavy  technical  terms 
and  the  formulae  of  the  higher  mathematics  have  been  avoided, 
yet  without  sacrificing  any  of  the  requirements  of  practical 
instruction;  the  arrangement  of  matter  is  such  as  to  carry  the 
reader  along  by  easy  steps  to  complete  mastery  of  each  subject; 
frequent  examples  for  practice  are  given,  to  enable  the  reader  to 
test  his  knowledge  and  make  it  a  permanent  possession;  and  the 
illustrations  are  selected  with  the  greatest  care  to  supplement  and 
make  clear  the  references  in  the  text. 

C.  The  method  adopted  in  the  preparation  of  these  volumes  is  that 
which  the  American  School  of  Correspondence  has  developed  and 
employed  so  successfully  for  many  years.  It  is  not  an  experiment, 
but  has  stood  the  severest  of  all  tests — that  of  practical  use — which 
has  demonstrated  it  to  be  the  best  method  yet  devised  for  the 
education  of  the  busy  working  man. 

C,  For  purposes  of  ready  reference  and  timely  information  when 
needed,  it  is  believed  that  this  series  of  handbooks  will  be  found  to 
meet  every  requirement. 


Table    of    Contents 


SYSTEMS  OF  HEATING ._    Page     1 

Stoves — Hot-Air  Furnaces — Direct  and  Indirect  Steam  Heating — Direct- 
Indirect  Radiators — Direct  and  Indirect  Hot-Water  Heating — Exhaust 
Steam  Heating — Forced  Blast  Heating — Electric  Heating — Principles  of 
Ventilation — Composition  of  Atmosphere — Quantity  of  Air  Required — Force 
for  Moving  Air — Measurements  of  Velocity — Air  Distribution — Heat  Loss 
from  Buildings 

DETAILS,  CARE,  AND  MANAGEMENT  OF  APPARATUS     .  .       ,.       Page    19 

Types  of  Furnaces  (Direct-  and  Indirect-Draft) — Furnace  Details  (Grate, 
Firepot,  Combustion  Chamber,  Radiator,  Heating  Surface,  Efficiency,  Heat- 
ing Capacity) — Location  of  Furnace — Smoke-Pipe — Chimney  Flue — Cold- 
Air  Box — Return  Duct — Warm-Air  Pipes — Registers — Combination  Sys- 
tems— Care  and  Management  of  Furnaces — Steam  Boilers  (Tubular  and 
Sectional) — Water-Tube  Boilers — Horse- Power  for  Ventilation — Radiators 
for  Direct  Steam  (Cast-Iron  and  Pipe) — Circulation  Coils — Efficiency  of 
Radiators,  Coils,  etc. — Systems  of  Piping  (Two-Pipe,  One-Pipe  Relief,  One- 
Pipe  Circuit) — Radiator  Connections — Expansion  of  Pipes — Valves  (Angle, 
Offset,  Corner,  Globe) — Air-Valves — Pipe  Sizes — Calculating  Flow  of  Steam 
— Calculating  Heating  Surface  Supplied — Boiler  Connections — Sizes  for  Re- 
turn, Blow-Off,  and  Feed  Pipes — Blow-Off  Tank — Types  of  Indirect-Steam 
Heaters — Efficiency  of  Heaters — Stacks,  and  Casings — Dampers — Warm-Air 
Flues — Cold-Air  Ducts — Vent  Flues — Registers — Pipe  Connections — Direct- 
Indirect  Radiators — Care  and  Management  of  Boilers — Types  of  Direct 
Hot-Water  Heaters — Direct  Hot-Water  Circulation — Direct  Hot-Water 
Radiators — Hot- Water  Piping — Overhead  Distribution — Expansion  Tank — 
Air-Venting — Hot-Water  Pipe  Connections — Valves  and  Fittings — Types  of 
Indirect  Hot-Water  Radiators — Size  of  Stacks — Flues  and  Casings — Care 
and  Management  of  Hot-Water  Heaters — Forced  Hot-WTater  Circulation — 
Single-Pipe  and  Circuit  Systems  of  Piping — Sizes  of  Mains  and  Branches — 
Pumps — Pipe  Flow — Friction  Head— Exhaust-Steam  Heating — Reducing 
Valves — Grease  Extractor  for  Exhaust  Steam — rBack-Pressure  Valve — Ex- 
haust Head — Return-Pumps — Balance  Pipe — Return  Traps — Damper  Regu- 
lators— Vacuum  or  Low-Pressure  Systems  (Webster,  Paul) 

SYSTEMS  OF  VENTILATION Page  147 

Forced  Blast  (Exhaust  and  Plenum  Methods) — Form  of  Heating  Surface — - 
Centrifugal  Fans  or  Blowers — Disc  Fans  or  Propellers — General  Proportions 
— Exhausters — Fan  Speeds  and  Pressures— Velocities  of  Air-Flow—Blast 
Area — Resistance — Power  Required — Capacity,  Speed,  etc.,  of  Disc  Fans — 
Fan  Engines  and  Motors — Factory  Heating — Double-Duct  System — Electric 
Heating — Calculation  and  Construction  of  Electric  Heaters — Temperature 
Regulators — Diaphragm  Motors — Dampers — Telethermometer — Humidostat 
— Air  Filters  and  Washers — Heating  and  Ventilating  of  Schools,  Hospitals, 
Churches,  Office  Buildings,  Apartment  Houses,  Conservatories,  etc. 

INDEX      , •       .      v      .       Page  215 


HOT    WATER    HEATER    AND    CONNECTIONS. 


HEATING  AND  VENTILATION 

PART  I 


SYSTEMS  OF  WARMING 

Any  system  of  warming  must  include,  first,  the  combustion 
of  fuel,  which  may  take  place  in  a  fireplace,  stove,  or  furnace,  or  a 
steam,  or  hot-water  boiler;  second,  a  system  of  transmission,  by  means 
of  which  the  heat  may  be  carried,  with  as  little  loss  as  possible,  to  the 
place  where  it  is  to  be  used  for  warming;  and  third,  a  system  of  dif- 
fusion, which  will  convey  the  heat  to  the  air  in  a  room,  and  to  its 
walls,  floors,  etc.,  in  the  most  economical  way. 

Stoves.  The  simplest  and  cheapest  form  of  heating  is  the  stove. 
The  heat  is  diffused  by  radiation  and  convection  directly  to  the  objects 
and  air  in  the  room,  and  no  special  system  of  transmission  is  required. 
The  stove  is  used  largely  in  the -country,  and  is  especially  adapted 
to  the  warming  of  small  dwelling-houses  and  isolated  rooms. 

Furnaces.  Next  in  cost  of  installation  and  in  simplicity  of 
operation,  is  the  hot-air  furnace.  In  this  method,  the  air  is  drawn 
over  heated  surfaces  and  then  transmitted  through  pipes,  while  at 
a  high  temperature,  to  the  rooms  where  heat  is  required.  Furnaces 
are  used  largely  for  warming  dwelling-houses,  also  churches,  halls, 
and  schoolhouses  of  small  size.  They  are  more  costly  than  stoves, 
but  have  certain  advantages  over  that  form  of  heating.  They  require 
less  care,  as  several  rooms  may  be  warmed  from  a  single  furnace; 
and,  being  placed  in  the  basement,  more  space  is  available  in  the 
rooms  above,  and  the  dirt  and  litter  connected  with  the  care  of  a  stove 
are  largely  done  away  with.  They  require  less  care,  as  only  one  fire 
is  necessary  to  warm  all  the  rooms  in  a  house  of  ordinary  size.  One 
great  advantage  in  the  furnace  method  of  warming  comes  from  the 
constant  supply  of  fresh  air  which  is  required  to  bring  the  heat  into 
the  rooms.  While  this  is  greatly  to  be  desired  from  a  sanitary  stand- 
point, it  calls  for  the  consumption  of  a  larger  amount  of  fuel  than 
would  otherwise  be  necessary.  This  is  true  because  heat  is  required 
to  warm  the  fresh  air  from  out  of  doors  up  to  the  temperature  of  the 


HEATING  AND  VENTILATION 


rooms,  in  addition  to  replacing  the  heat  lost  by  leakage  and  conduction 
through  walls  and  windows. 

A  more  even  temperature  may  be  maintained  with  a  furnace 
than  by  the  use  of  stoves,  owing  to  the  greater  depth  and  size  of  the 
fire,  which  allows  it  to  be  more  easily  controlled. 

When  a  building  is  placed  in  an  exposed  location,  there  is  often 
difficulty  in  warming  rooms  on  the  north  and  west  sides,  or  on  that 
side  toward  the  prevailing  winds.  This  may  be  overcome  to  some  ex- 
tent by  a  proper  location  of  the  furnace  and  by  the  use  of  extra  large 
pipes  for  conveying  the  hot  air  to  those  rooms  requiring  special  at- 
tention. 

Direct  Steam.  Direct  steam,  so  called,  is  widely  used  in  all 
classes  of  buildings,  both  by  itself  and  in  combination  with  other 
systems.  The  first  cost  of  installation  is  greater  than  for  a  furnace; 
but  the  amount  of  fuel  required  is  less,  as  no  outside  air  supply  is 
necessary.  If  used  for  warming  hospitals,  schoolhouses,  or  other 
buildings  where  a  generous  supply  of  fresh  air  is  desired,  this  method 
must  be  supplemented  by  some  form  of  ventilating  system. 

One  of  the  principal  advantages  of  direct  steam  is  the  ability 
to  heat  all  rooms  alike,  regardless  of  their  location  or  of  the  action 
of  winds. 

When  compared  with  hot-water  heating,  it  has  still  another 
desirable  feature — which  is  its  freedom  from  damage  by  the  freezing 
of  water  in  the  radiators  when  closed,  which  is  likely  to  happen  in 
unused  rooms  during  very  cold  weather  in  the  case  of  the  former 
system. 

On  the  other  hand,  the  sizes  of  the  radiators  must  be  proportioned 
for  warming  the  rooms  in  the  coldest  weather,  and  unfortunately 
there  is  no  satisfactory  method  of  regulating  the  amount  of  heat  in 
mild  weather,  except  by  shutting  off  or  turning  on  steam  in  the  radia- 
ators  at  more  or  less  frequent  intervals  as  may  be  required,  unless  one 
of  the  expensive  systems  of  automatic  control  is  employed.  In  large 
rooms,  a  certain  amount  of  regulation  can  be  secured  by  dividing 
the  radiation  into  two  or  more  parts,  so  that  different  combinations 
may  be  used  under  varying  conditions  of  outside  temperature.  If 
two  radiators  "are  used,  their  surface  should  be  proportioned,  when 
convenient,  in  the  ratio  of  1  to  2,  in  which  case  one-third,  two-thirds, 
or  the  whole  power  of  the  radiation  can  be  used  as  desired. 


HEATING  AND  VENTILATION 


Indirect  Steam.  This  system  of  heating  combines  some  of  the 
advantages  of  both  the  furnace  and  direct  steam,  but  is  more  costly 
to  install  than  either  of  these.  The  amount  of  fuel  required  is  about 
the  same  as  for  furnace  heating,  because  in  each  case  the  cool  fresh 
air  must  be  warmed  up  to  the  temperature  of  the  room,  before  it  can 
become  a  medium  for  conveying  heat  to  offset  that  lost  by  leakage 
and  conduction  through  walls  and  windows. 

A  system  for  indirect  steam  may  be  so  designed  that  it  will  supply 
a  greater  quantity  of  fresh  air  than  the  ordinary  form  of  furnace,  in 
which  case  the  cost  of  fuel  will  of  course  be  increased  in  proportion  to 
the  volume  of  air  supplied.  Instead  of  placing  the  radiators  in  the 
rooms,  a  special  form  of  heater  is  supported  near  the  basement  ceiling 
and  encased  in  either  galvanized  iron  or  brick.  A  cold-air  supply 
duct  is  connected  with  the  space  below  the  heater,  and  warm  air  pipes 
are  taken  from  the  top  and  connected  with  registers  in  the  rooms  to 
be  heated  the  same  as  in  the  case  of  furnace  heating. 

A  separate  stack  or  heater  may  be  provided  for  each  register  if 
the  rooms  are  large;  but,  if  small  and  so  located  that  they  may  be 
reached  by  short  runs  of  horizontal  pipe,  a  single  heater  may  serve 
for  two  or  more  rooms. 

The  advantage  of  indirect  steam,  over  furnace  heating  comes  from 
the  fact  that  the  stacks  may  be  placed  at  or  near  the  bases  of  the  flues 
leading  to  the  different  rooms,  thus  doing  away  with  long,  horizontal 
runs  of  pipe,  and  counteracting  to  a  considerable  extent  the  effect  of 
wind  pressure  upon  exposed  rooms.  Indirect  and  direct  heating  are 
often  combined  to  advantage  by  using  the  former  for  the  more  import- 
ant rooms,  where  ventilation  is  desired,  and  the  latter  for  rooms  more 
remote  or  where  heat  only  is  required. 

Another  advantage  is  the  large  ratio  between  the  radiating  sur- 
face and  grate-area,  as  compared  with  a  furnace ;  this  results  in  a  large 
volume  of  air  being  warmed  to  a  moderate  temperature  instead  of  a 
smaller  quantity  being  heated  to  a  much  higher  temperature,  thus 
giving  a  more  agreeable  quality  to  the  air  and  rendering  it  less  dry. 

Indirect  steam  is  adapted  to  all  the  buildings  mentioned  in  con- 
nection with  furnace  heating,  and  may  be  used  to  much  better  advan- 
tage in  those  of  large  size.  This  applies  especially  to  cases  where 
more  than  one  furnace  is  necessary;  for,  with  steam  heat,  a  single 
boiler,  or  a  battery  of  boilers,  may  be  made  to  supply  heat  for  a  build- 


HEATING  AND  VENTILATION 


ing  of  any  size,  or  for  a  group  of  several  buildings,  if  desired,  and  is 
much  easier  to  care  for  than  several  furnaces  widely  scattered. 

Direct-Indirect  Radiators.  These  radiators  are  placed  in  the 
room  the  same  as  the  ordinary  direct  type.  The  construction  is  such 
that  when  the  sections  are  in  place,  small  flues  are  formed  between 
them;  and  air,  being  admitted  through  an  opening  in  the  outside  wall, 
passes  upward  through  them  and  becomes  heated  before  entering  the' 
room.  A  switch  damper  is  placed  in  the  casing  at  the  base  of  the 
radiator,  so  that  air  may  be  taken  from  the  room  itself  instead  of 
from  out  of  doors,  if  so  desired.  Radiators  of  this  kind  are  not  used 
to  any  great  extent,  as  there  is  likely  to  be  more  or  less  leakage  of  cold 
air  into  the  room  around  the  base.  If  ventilation  is  required,  it  is 
better  to  use  the  regular  form  of  indirect  heater  with  flue  and  register, 
if  possible.  It  is  sometimes  desirable  to  partially  ventilate  an  isolated 
room  where  it  would  be  impossible  to  run  a  flue,  and  in  cases  of  this 
kind  the  direct-indirect  form  is  often  useful. 

Direct  Hot  Water.  Hot  water  is  especially  adapted  to  the  warm- 
ing of  dwellings  and  greenhouses,  owing  to  the  ease  with  which  the 
temperature  can  be  regulated.  When  steam  is  used,  the  radiators  are 
always  at  practically  the  same  temperature,  while  with  hot  water  the 
temperature  can  be  varied  at  will.  A  system  for  hot-water  heating 
costs  more  to  install  than  one  for  steam,  as  the  radiators  must  be  larger 
and  the  pipes  more  carefully  run.  On  the  other  hand,  the  cost  of 
operating  is  somewhat  less,  because  the  water  need  be  carried  only  at 
a  temperature  sufficiently  high  to  warm  the  rooms  properly  in  mild 
weather,  while  with  steam  the  building  is  likely  to  become  overheated, 
and  more  or  less  heat  wasted  through  open  doors  and  windows. 

A  comparison  of  the  relative  costs  of  installing  and  operating  hot- 
air,  steam,  and  hot-water  systems,  is  given  in  Table  I. 

TABLE  I 
Relative  Cost  of  Heating  Systems 


. 

HOT  AIR 

STEAM 

HOT  WATEH 

Relative  cost  of  apparatus 

9 

13 

15 

Relative  cost,  adding  repairs  and  fuel 

for  five  years 

29  i 

29| 

27 

Relative  cost,  adding  repairs  and  fuel  for 

fifteen  years 

81 

63 

52£ 

HEATING  AND  VENTILATION 


One  disadvantage  in  the  use  of  hot  water  is  the  danger  from 
freezing  when  radiators  are  shut  off  in  unused  rooms.  This  makes 
it  necessary  in  very  cold  weather  to  have  all  parts  of  the  system  turned 
on  sufficiently  to  produce  a  circulation,  even  if  very  slow.  This  is 
sometimes  accomplished  by  drilling  a  very  small  hole  (about  J  inch) 
in  the  valve-seat,  to  that  when  closed  there  will  still  be  a  very  slow 
circulation  through  the  radiator,  thus  preventing  the'temperature  of 
the  water  from  reaching  the  freezing  point. 

Indirect  Hot  Water.  This  is  used  under  the  same  conditions  as 
indirect  steam,  but  more  especially  in  the  case  of  dwellings  and  hospi- 
tals. When  applied  to  other  and  larger  buildings,  it  is  customary  to 
force  the  water  through  the  mains  by  means  of  a  pump.  Larger 
heating  stacks  and  supply  pipes  are  required  than  for  steam;  but  the 
arrangement  and  size  of  air-flues  and  registers  are  practically  the 
same,  although  they  are  sometimes  made  slightly  larger  in  special  cases, 

Exhaust  Steam.  Exhaust  steam  is  used  for  heating  in  connection 
with  power  plants,  as  in  shops  and  factories,  Or  in  office  buildings 
which  have  their  own  lighting  plants.  There  are  two  methods  of 
using  exhaust  steam  for  heating  purposes.  One  is  to  carry  a  back 
pressure  of  2  to  5  pounds  on  the  engines,  depending  upon  the  length 
and  size  of  the  pipe  mains ;  and  the  other  is  to  use  some  form  of  vacuum 
system  attached  to  the  returns  or  air-valves,  which  tends  to  reduce 
the  back  pressure  rather  than  to  increase  it. 

Where  the  first  method  is  used  and  a  back  pressure  carried,  either 
the  boiler  pressure  or  the  cut-off  of  the  engines  must  be  increased,  to 
keep  the  mean  effective  pressure  the  same  and  not  reduce  the  horse- 
power delivered.  In  general  it  is  more  economical  to  utilize  the  ex- 
haust steam  for  heating.  There  are  instances,  however,  where  the 
relation  between  the  quantities  of  steam  required  for  heating  and  for 
power  are  such — especially  if  the  engines  are  run  condensing — that 
it  is  better  to  throw  the  exhaust  away  and  heat  with  live  steam. 
Where  the  vacuum  method  is  used,  these  difficulties  are  avoided ;  and 
for  this  reason  that  method  is  coming  into  quite  common  use. 
If  the  condensation  from  the  exhaust  steam  is  returned  to  the 
boilers,  the  oil  must  first  be  removed ;  this  is  usually  accomplished  by 
passing  the  steam  through  some  form  of  grease  extractor  as  it  leaves 
the  engine.  The  water  of  condensation  is  often  passed  through  a 
separating  tank  in  addition  to  this,  before  it  is  delivered  to  the  return 


HEATING  AND  VENTILATION 


pumps.  It  is  better,  however,  to  remove  a  portion  of  the  oil  before 
the  steam  enters  the  heating  system ;  otherwise  a  coating  will  be  formed 
upon  the  inner  surfaces  of  the  radiators,  which  will  reduce  their 
efficiency  to  some  extent. 

Forced  Blast.  This  method  of  heating,  in  different  forms,  is 
used  for  the  warming  of  factories,  schools,  churches,  theaters,  halls — 
in  fact,  any  large  building  where  good  ventilation  is  desired.  The 
air  for  warming  is  drawn  or  forced  through  a  heater  of  special  design, 
and  discharged  by  a  fan  or  blower  into  ducts  which  lead  to  registers 
placed  in  the  rooms  to  be  warmed.  The  heater  is  usually  made  up  in 
sections,  so  that  steam  may  be  admitted  to  or  shut  off  from  any  section 
independently  of  the  others,  and  the  temperature  of  the  air  regulated 
in  this  manner.  Sometimes  a  by-pass  damper  is  attached,  so  that 
part  of  the  air  will  pass  through  the  heater  and  part  around  or  over  it ; 
in  this  way  the  proportions  of  cold  and  heated  air  may  be  so  adjusted 
as  to  give  the  desired  temperature  to  the  air  entering  the  rooms.  These 
forms  of  regulation  are  common  where  a  blower  is  used  for  warming 
a  single  room,  as  in  the  case  of  a  church  or  hall;  but  where  several 
rooms  are  warmed,  as  in  a  schoolhouse.  it  is  customary  to  use  the 
main  or  primary  heater  at  the  blower  for  warming  the  air  to  a  given 
temperature  (somewhat  below  that  which  is  actually  required),  and 
to  supplement  this  by  placing  secondary  coils  or  heaters  at  the  bottoms 
of  the  flues  leading  to  the  different  rooms.  By  means  of  this  arrange- 
ment, the  temperature  of  each  room  can  be  regulated  independently 
of  the  others.  The  so-called  double-duct  system  is  sometimes  employed. 
In  this  case,  two  ducts  are  carried  to  each  register,  one  supplying  hot 
air  and  the  other  cold  or  tempered  air;  and  a  damper  for  mixing  these 
in  the  right  proportions  is  placed  in  the  flue,  below  the  register. 

Electric  Heating.  Unless  electricity  can  be  produced  at  a'  very 
low  cost,  it  is  not  practicable  for  heating  residences  or  large  buildings. 
The  electric  heater,  however,  has  quite  a  wide  field  of  application  in 
heating  small  offices,  bathrooms,  electric  cars,  etc.  It  is  a  convenient 
method  of  warming  isolated  rooms  on  cold  mornings,  in  late  spring  and 
early  fall,  when  the  regular  heating  apparatus  of  the  building  is  not  in 
operation.  It  has  the  advantage  of  being  instantly  available,  and  the 
amount  of  heat  can  be  regulated  at  will.  Electric  heaters  are  clean, 
do  not  vitiate  the  air,  and  are  easily  moved  from  place  to  place. 


HEATING  AND  VENTILATION 


PRINCIPLES    OF   VENTILATION 

Closely  connected  with  the  subject  of  heating  is  the  problem  of 
maintaining  air  of  a  certain  standard  of  purity  in  the  various  buildings 
occupied.  ^ 

The  introduction  of  pure  air  can  be  done  properly  only  in  con- 
nection with  some  system  of  heating;  and  no  system  of  heating  is 
complete  without  a  supply  of  pure  air,  depending  in  amount  upon  the 
kind  of  building  and  the  purpose  for  which  it  is  used. 

Composition  of  the  Atmosphere.  Atmospheric  air  is  not  a  simple 
substance  but  a  mechanical  mixture.  Oxygen  and  nitrogen;  the 
principal  constituents,  are  present  in  very  nearly  the  proportion  of  one 
part  of  oxygen  to  four  parts  of  nitrogen  by  weight.  Carbonic  acid  gas, 
the  product  of  all  combustion,  exists  in  the  proportion  of  3  to  5  parts 
in  10,000  in  the  open  country.  Water  in  the  form  of  vapor,  varies 
greatly  with  the  temperature  and  with  the  exposure  of  the  air  to  open 
boclies  of  water.  In  addition  to  the  above,  there  are  generally  present, 
in  variable  but  exceedingly  small  quantities,  ammonia,  sulphuretted 
hydrogen,  sulphuric,  sulphurous,  .nitric,  and  nitrous  acids,  floating 
organic  and  inorganic  matter,  and  local  impurities.  Air  also  contains 
ozone,  which  is  a  peculiarly  active  form  of  oxygen ;  and  lately  another 
constituent  called  argon  has  been  discovered. 

Oxygen  is  the  most  important  element  of  the  air,  so  far  as  both 
heating  and  ventilation  are  concerned.  It  is  the  active  element  in  the 
chemical  process  of  combustion  and  also  in  the  somewhat  similar 
process  which  takes  place  in  the  respiration  of  human  beings.  Taken 
into  the  lungs,  it  acts  upon  the  excess  of  carbon  in  the  blood,  and  pos- 
sibly upon  other  ingredients,  forming  chemical  compounds  which  are 
thrown  off  in  the  act  of  respiration  or  breathing. 

Nitrogen.  The  principal  bulk  of  the  atmosphere  is  nitrogen, 
which  exists  uniformly  diffused  with  oxygen  and  carbonic  acid  gas. 
This  element  is  practically  inert  in  all  processes  of  combustion  or 
respiration.  It  is  not  affected  in  composition,  either  by  passing  through 
a  furnace  during  combustion  or  through  the  lungs  in  the  process  of 
respiration.  Its  action  is  to  render  the  oxygen  less  active,  and  to 
absorb  some  part  of  the  heat  produced  by  the  process  of  oxidation. 

Carbonic  acid  gas  is  of  itself  only  a  neutral  constituent  of  the 
atmosphere,  like  nitrogen ;  and — contrary  to  the  general  impression — 
its  presence  in  moderately  large  quantities  (if  uncombined  with  other 


HEATING  AND  VENTILATION 


substances)  is  neither  disagreeable  nor  especially  harmful.  Its 
presence,  however,  in  air  provided  for  respiration,  decreases  the  readi- 
ness with  which  the  carbon  of  the  blood  unites  with  the  oxygen  of  the 
air;  and  therefore,  when  present  in  sufficient  quantity,  it  may  cause 
indirectly,  not  only  serious,  but  fatal  results.  The  real  harm  of  a 
vitiated  atmosphere,  however,  is  caused  by  the  other  constituent 
gases  and  by  the  minute  organisms  which  are  produced  in  the  process 
of  respiration.  It  is  known  that  these  other  impurities  exist  in  fixed 
proportion  to  the  amount  of  carbonic  acid  present  in  an  atmosphere 
vitiated  by  respiration.  Therefore,  as  the  relative  proportion  of 
carbonic  acid  can  easily  be  determined  by  experiment,  the  fixing  of  a 
standard  limit  of  the  amount  in  which  it  may  be  allowed,  also  limits  the 
amounts  of  other  impurities  which  are  found  in  combination  with  it. 

When  carbonic  acid  is  present  in  excess  of  10  parts  in  10,000 
parts  of  air,  a  feeling  of  weariness  and  stuffiness, generally  accompanied 
by  a  headache,  will  be  experienced;  while  with  even  8  parts  in  10,000 
parts  a  room  would  be  considered  close.  For  general  considerations 
of  ventilation,  the  limit  should  be  placed  at  6  to  7  parts  in  10,000,  thus 
allowing  an  increase  of  2  to  3  parts  over  that  present  in  outdoor  air, 
which  may  be  considered  to  contain  four  parts  in  10,000  under  ordi- 
nary conditions. 

Analysis  of  Air.  An  accurate  qualitative  and  quantitative 
analysis  of  air  samples  can  be  made  only  by  an  experienced  chemist. 
There  are,  however,  several  approximate  methods  for  determining 
the  amount  of  carbonic  acid  present,  which  are  sufficiently  exact  for 
practical  purposes.  Among  these  the  following  is  one  of  the  simplest : 

The  necessary  apparatus  consists  of  six  clean,  dry,  and  tightly 
corked  bottles,  containing  respectively  100, 200, 250, 300, 350,  and  400 
cubic  centimeters,  a  glass  tube  containing  exactly  15  cubic  centimeters 
to  a  given  mark,  and  a  bottle  of  perfectly  clear,  fresh  limewater.  The 
bottles  should  be  filled  with  the  air  to  be  examined  by  means  of  a  hand- 
ball syringe.  Add  to  the  smallest  bottle  15  cubic  centimeters  of  the 
limewater,  put  in  the  cork,  and  shake  well.  If  the  limewater  has  a 
milky  appearance,  the  amount  of  carbonic  acid  will  be  at  least  16 
parts  in  10,000.  If  the  contents  of  the  bottle  remain  clear,  treat  the 
bottle  of  200  cubic  centimeters  in  the  same  manner;  a  milky  appear- 
ance or  turbidity  in  this  would  indicate  12  parts  in  10,000.  In  a 
similar  manner,  turbidity  in  the  250  cubic  centimeter  bottle  indicates 


HEATING  AND  VENTILATION  9 

10  parts  in  10,000;  in  the  300,  8  parts;  in  the  350,  7  parts;  and  in  the 
400,  less  than  6  parts.  The  ability  to  conduct  more  accurate  analyses 
can  be  attained  only  by  special  study  and  a  knowledge  of  chemical 
properties  and  of  methods  of  investigation. 

Another  method  similar  to  the  above,  makes  use  of  a  glass 
cylinder  containing  a  given  quantity  of  limewater  and  provided  with  a 
piston.  A  sample  of  the  air  to  be  tested  is  drawn  into  the  cylinder  by 
an  upward  movement  of  the  piston.  The  cylinder  is  then  thoroughly 
shaken,  and  if  the  limewater  shows  a  milky  appearance,  it  indicates 
a  certain  proportion  of  carbonic  acid  in  the  air.  If  the  limewater 
remains  clear,  the  air  is  forced  out,  and  another  cylinder  full  drawn  in, 
the  operation  being  repeated  until  the  limewater  becomes  milky. 
The  size  of  the  cylinder  and  the  quantity  of  limewater  are  so  propor- 
tioned that  a  change  in  color  at  the  first,  second,  third,  etc.,  cylinder 
full  of  air  indicafes  different  proportions  of  carbonic  acid.  This  test 
is  really  the  same  in  principle  as  the  one  previously  described;  but  the 
apparatus  used  is  in  more  convenient  form. 

Air  Required  for  Ventilation.  The  amount  of  air  required  to 
maintain  any  given  standard  of  purity  can  very  easily  be  determined, 
provided  we  know  the  amount  of  carbonic  acid  given  off  in  the  process 
of  respiration.  It  has  been  found  by  experiment  that  the  average 
production  of  carbonic  acid  by  an  adult  at  rest  is  about  .6  cubic  foot 
per  hour.  If  we  assume  the  proportion  of  this  gas  as  4  parts  in  10,000 
in  the  external  air,  and  are  to  allow  6  parts  in  10,000  in  an  occupied 

room,  the  gain  will  be  2  parts  in  10,000;  or,  in  other  words,  there  will 

2 
be  TTTTT  =  .0002  cubic  foot  of  carbonic  acid  mixed  with  each  cubic 


foot  of  fresh  air  entering  the  room.  Therefore,  if  one  person  gives 
off  .6  cubic  foot  of  carbonic  acid  per  hour,  it  will  require  .6  -f-  .0002 
=  3,000  cubic  feet  of  air  per  hour  per  person  to  keep  the  air  in  the 
room  at  the  standard  of  purity  assumed  —  that  is,  6  parts  of  carbonic 
acid  in  10,000  of  air. 

Table  II  has  been  computed  in  this  manner,  and  shows  the 
amount  of  air  which  must  be  introduced  for  each  person  in  order  to 
maintain  various  standards  of  purity. 

While  this  table  gives  the  theoretical  quantities  of  air  required 
for  different  standards  of  purity,  and  may  be  used  as  a  guide,  it  will  be 
better  in  actual  practice  to  use  quantities  which  experience  has  shown 


10 


HEATING  AND  VENTILATION 


to  give  good  results  in  different  types  of  buildings.  In  auditoriums 
where  the  cubic  space  per  individual  is  large,  and  in  which  the  atmos- 
phere is  thoroughly  fresh  before  the  rooms  are  occupied,  and^the 
occupancy  is  of  only  two  or  three  hours'  duration,  the  air-supply  may 
be  reduced  somewhat  from  the  figures  given  below. 

TABLE  II 
Quantity  of  Air  Required  per  Person 


STANDARD  PARTS  OP  CARBONIC 
ACID  IN  10,000  OF  AIR 


CUBIC  FEET  OP  AIR  REQUIRED  PER  PERSON 


IN  ROOM 

Per  Minute 

Per  Hour 

5 

100 

6,000 

6 

50 

3,000 

7 

33 

2,000 

8 

25 

1,500 

9 

20 

1,200 

10 

16 

1,000 

Table  III  represents  good  modern  practice  and  may  be  used 
with  satisfactory  results : 

TABLE  III 
Air  Required  for  Ventilation  of  Various  Classes  of  Buildings 


AIR-SUPPLY  PER  OCCUPANT  FOR 

CUBIC  FEET  PER 
MINUTE 

CUBIC  FEET  PER 
HOUR 

Hospitals 
High  Schools 
Grammar  Schools 
Theaters  and  Assembly  Halls 
Churches 

80  to  100 
50 
40 
25 
20 

4,  800  to  6,  000 
3,000 
2,400 
1,500 
1,200 

When  possible,  the  air-supply  to  any  given  room  should  be  based 
upon  the  number  of  occupants.  It  sometimes  happens,  however, 
that  this  information  is  not  available,  or  the  character  of  the  room  is 
such  that  the  number  of  persons  occupying  it  may  vary,  as  in  the  case 
of  public  waiting  rooms,  toilet  rooms,  etc.  In  instances  of  this  kind, 
the  requireH  air-volume  may  be  based  upon  the  number  of  changes 
per  hour.  In  using  this  method,  various  considerations  must  be  taken 
into  account,  such  as  the  use  of  the  room  and  its  condition  as  to  crowd- 
ing, character  of  occupants,  etc.  In  general,  the  following  will  be 
found  satisfactory  for  average  conditions : 


HEATING  AND  VENTILATION 


11 


TABLE  IV 
Number  of  Changes  of  Air  Required  in  Various  Rooms 


USE  OF  ROOM 

CHANGES  op 

A.IR  PER  HOUR 

Public  Waiting  Room      *" 

4t 

o5 

Public  Toilets 

5 

6 

Coat  and  Locker  Rooms 

4 

5 

Museums 

3 

4 

Offices,  Public 

4 

5 

Offices,  Private 

3 

4 

Public  Dining  Rooms 

4 

5 

Living  Rooms* 

3 

4 

Libraries,  Public 

4 

5 

Libraries,  Private 

3 

4 

Force  for  Moving  Air.  Air  is  moved  for  ventilating  purposes  in 
two  ways:  (1)  by  expansion  due  to  heating;  (2)  by  mechanical  means. 
The  effect  of  heat  on  the  air  is  to  increase  its  volume  and  therefore 
lessen  its  density  or  weight,  so  that  it  tends  to  rise  and  is  replaced  by 
the  colder  air  below.  The  available  force  for  moving  air  obtained  in 
this  way  is  very  small,  and  is  quite  likely  to  be  overcome  by  wind  or 
external  causes.  It  will  be  found  in  general  that  the  heat  used  for 
producing  Velocity  in  this  manner,  when  transformed  into  work  in 
the  steam  engine,  is  greatly  in 
excess  of  that  required  to  pro- 
duce the  same  effect  by  the  use  of 
a  fan. 

Ventilation  by  mechanical 
means  is  performed  either  by 
pressure  or  by  suction.  The  for- 
mer is  used  for  delivering  fresh  air 
into  a  building,  and  the  latter  for 
removing  the  foul  air  from  it. 

By  both  processes  the  air  is  moved     Fig.  1.    Common  Form  of  Anemometer,  for 
. . ,  ,  .  Measuring  Velocity  of  Air-Currents. 

without  change   in  temperature, 

and  the  force  for  moving  must  be  sufficient  to  overcome  the  effects 
of  wind  or  changes  in  outside  temperature.  Some  form  of  fan  is  used 
for  this  purpose. 

Measurements  of  Velocity.  The  velocity  of  air  in  ventilating 
ducts  and  flues  is  measured  directly  by  an  instrument  called  an  ane- 
mometer. A  common  form  of  this  instrument  is  shown  in  Fig.  1.  It 
consists  of  a  series  of  flat  vanes  attached  to  an  axis,  and  a  series  of  dials. 


12  HEATING  AND  VENTILATION 


The  revolution  of  the  axis  causes  motion  of  the  hands  in  proportion  to 
the  velocity  of  the  air,  and  the  result  can  be  read  directly  from  the  dials 
for  any  given  period. 

For  approximate  results  the  anemometer  may  be  slowly  moved 
across  the  opening  in  either  vertical  or  horizontal  parallel  lines,,  so 
that  the  readings  will  be  made  up  of  velocities  taken  from  all  parts  of 
the  opening.  For  more  accurate  work,  the  opening  should  be  divided 
into  a  number  of  squares  by  means  of  small  twine,  and  readings  taken 
at  the  center  of  each.  The  mean  of  these  readings  will  give  the 
average  velocity  of  the  air  through  the  entire  opening. 

AIR  DISTRIBUTION 

The  location  of  the  air  inlet  to  a  room  depends  upon  the  size  of 
the  room  and  the  purpose  for  which  it  is  used.  In  the  case  of  living 
rooms  in  dwelling-houses,  the  registers  are  placed  either  in  the  floor 
or  in  the  wall  near  the  floor;  this  brings  the  warm  air  in  at  the  coldest 
part  of  the  room  and  gives  an  opportunity  for  warming  or  drying  the 
feet  if  desired.  In  the  case  of  schoolrooms,  where  large  volumes  of 
warm  air  at  moderate  temperatures  are  required,  it  is  best  to  discharge 
it  through  openings  in  the  wall  at  a  height  of  7  or  8  feet  from  the  floor ; 
this  gives  a  more  even  distribution,  as  the  warmer  air  tends  to  rise  and 
hence  spreads  uniformly  under  the  ceiling;  it  then  gradually  displaces 
other  air,  and  the  room  becomes  filled  with  pure  air  without  sensible 
currents  or  drafts.  The  cooler  air  sinks  to  the  bottom  of  the  room,  and 
can  be  taken  off  through  ventilating  registers  placed  near  the  floor. 
The  relative  positions  of  the  inlet  and  outlet  are  often  governed  to 
some  extent  by  the  building  construction ;  but,  if  possible,  they  should 
both  be  located  in  the  same  side  of  the  room.  Figs.  2,  3,  and  4  show 
common  arrangements. 

The  vent  outlet  should  always,  if  possible,  be  placed  in  an  inside 
wall;  otherwise  it  will  become  chilled  and  the  air-flow  through  it  will 
become  sluggish.  In  theaters  and  churches  which  are  closely  packed, 
the  air  should  enter  at  or  near  the  floor,  in  finely-divided  streams ;  and 
the  discharge  ventilation  should  be  through  openings  in  the  ceiling. 
The  reason  for  this  is  the  large  amount  of  animal  heat  given  off  from 
the  bodies  of  the  audience ;  this  causes  the  air  to  become  still  further 
heated  after  entering  the  room,  and  the  tendency  is  to  rise  continuously 


HEATING  AND  VENTILATION 


13 


from  floor  to  ceiling,  thus  carrying  away  all  impurities  from  respiration 
as  fast  as  they  are  given  off. 

All  audience  halls  in  which  the  occupants  are  closely  seated  should 
be  treated  in  the  same  manner,  when  possible.  This,  however,  can- 
*not  always  be  done,  afs  the  seats  are  often  made  removable  so  that  the 


•l 


OUTSIDE    WALL  OUTSIDE  WALL  OUTSIDE  WALL 

Fig.  2.  Fig.  3.  Fig.  4. 

Diagrams  Showing  Relative  Positions  of  Air  Inlets  and  Outlets  as  Commonly  Arranged. 

floor  can  be  used  for  other  purposes.  In  cases  of  this  kind,  part  of 
the  air  may  be  introduced  through  floor  registers  placed  along  the  outer 
aisles,  and  the  remainder  by  means  of  wall  inlets  the  same  as  for  school- 
rooms. The  discharge  ventilation  should  be  partly  through  registers 
near  the  floor,  supplemented  by  ample  ceiling  vents  for  use  when  the 
hall  is  crowded  or  the  outside  temperature  high. 

The  matter  of  air-velocities,  size  of  flues,  etc.,  will  be  taken  up 
under  the  head  of  "Indirect  Heating." 

HEAT  LOSS  FROM  BUILDINGS 

A  British  Thermal  Unit,  or  B.  T.  U.,  has  been  defined  as  the 
amount  of  heat  required  to  raise  the  temperature  of  one  pound  of 
water  one  degree  F.  This  measure  of  heat  enters  into  many  of  the 
calculations  involved  in  the  solving  of  problems  in  heating  and  ventila- 
tion, and  one  should  familiarize  himself  with  the  exact  meaning  of 
the  term. 

Causes  of  Heat  Loss.  The  heat  loss  from  a  building  is  due  to 
the  following  causes:  (1)  radiation  and  conduction  of  heat  through 
walls  and  windows;  (2)  leakage  of  warm  air  around  doors  and  win- 
dows and  through  the  walls  themselves;  and  (3)  heat  required  to  warm 
the  air  for  ventilation. 

Loss  through  Walls  and  Windows.  The  loss  of  heat  through 
the  walls  of  a  building  depends  upon  the  material  used  in  construction 


14 


HEATING  AND  VENTILATION 


TABLE  V 

Heat  Losses  in  B.  T.  U.  per  Square  Foot  of  Surface  per  Hour- 
Southern  Exposure 


MATERIAL 

DIFFERENCE   BETWEEN     INSIDE    AND    OUT- 
SIDE TEMPERATURES 

10° 

5 
4 
3 
2.8 
2.5 
2 
1.5 
12 
8 
11 
7 
4 
3 
6 
5 
2 
1.5 
1 

3 

20° 

30° 

40° 

18 
13 
10 
9 
8 
7 
6 
49 
32 
42 
28 
16 
11 
24 
20 
9 
6 
4 

10 

50° 

60° 

27 
20 
16 
14 
12 
11 
10 
73 
48 
63 
42 
24 
17 
36 
30 
13 
9 
6 

16 

70° 

31 

23 
19 
16 
14 
13 
11 
85 
56 
73 
48 
28 
20 
42 
35 
15 
10 
7 

19 

80° 

90° 

40 
30 
24 
20 
18 
16 
15 
110 
70 
94 
62 
36 
25 
54 
45 
20 
13 
9 

24 

100° 

45 
33 
27 
23 
20 
18 
16 
122 
78 
104 
70 
40 
28 
60 
50 
22 
15 
10 

27 

8-in  Brick  Wall 

9 
7 
5 
4.5 
4 
3.5 
3 
24 
16 
21 
14 
8 
5 
12 
10 
4 
3 
2 

5 

13 
10 
8 
7 
6 
5 
4.5 
36 
24 
31 
20 
12 
8 
18 
15 
6.5 
4.5 
3 

8 

22 
16 
13 
11 
10 
9 
8 
60 
40 
52 
35 
20 
14 
30 
25 
11 

f 
t 

13 

36 

26 
22 
18 
16 
14 
13 
93 
62 
-  84 
56 
32 
23 
48 
40 
18 
12 
8 

22 

12-in  Brick  Wall 

16-in  Brick  Wall 

20-in  Brick  Wall 

24-in  Brick  Wall 

28-in  Brick  Wall 

32-in  Brick  Wall 

Single  \Vindow 

Double  Window    

Single  Skylight 

Double  Skylight 

1-in  \Voodcn  Door 

2-in  \Vooden  Door 

2-in  Solid  Plaster  Partition 

3-in  Solid  Plaster  Partition 

Concrete  Floor  on  Brick  Arch  .... 
\Vood  Floor  on  Brick  ./Trch 

Double  Wood  Floor 

Walls  of  Ordinary  Wooden 
Dwellings   

For  solid  stone  watts,  multiply  the  figures  for  brick  of  the  same  thickness 
by  1.7.  Where  rooms  have  a  cold  attic  above  or  cellar  beneath,  multiply  the 
heat  loss  through  walls  and  windows  by  1 . 1 . 

Correction  for  Leakage.  The  figures  given  in  the  above  table  apply  only 
to  the  most  thorough  construction.  For  the  average  well-built  house,  the 
results  should  be  increased  about  10  per  cent;  for  fairly  good  construction, 
20  per  cent;  and  for  poor  construction,  30  per  cent. 

Table  V  applies  only  to  a  southern  exposure;  for  other  exposures  multi- 
ply the  heat  loss  given  in  Table  V  by  the  factors  given  in  Table  VI. 

of  the  wall,  the  thickness,  the  number  of  layers,  and  the  difference 
between  the  inside  and  outside  temperatures.  The  exact  amount  of 
heat  lost  in  this  way  is  very  difficult  to  determine  theoretically,  hence 
we  depend  principally  on  the  results  of  experiments. 

Loss  by  Air-Leakage.  The  leakage  of  air  from  a  room  varies 
from  one  to.  two  or  more  changes  of  the  entire  contents  per  hour, 
depending  upon  the  construction,  opening  of  doors,  etc.  It  is  com- 
mon practice  to  allow  for  one  change  per  hour  in  well-constructed 
buildings  where  two  walls  of  the  room  have  an  outside  exposure.  As 
the  amount  of  leakage  depends  upon  the  extent  of  exposed  wall  and 
window  surface,  the  simplest  way  of  providing  for  this  is  to  increase 


HEATING  AND  VENTILATION 


15 


TABLE  VI 
Factors  lor  Calculating  Heat  Loss  for  Other  than  Southern  Exposures 


EXPOSURE 

FACTOR 

N.    ^ 

.32 

E. 

.12 

S. 

.0 

w. 

.20 

N.E. 

.22 

N.  W. 

.26 

8.E. 

.06 

S.W. 

.10 

N.,  E.,  S.,  and  W.,  or  total  exposure 

1.16 

the  total  loss  through  walls  and  windows  by  a  factor  depending  upon 
the  tightness  of  the  building  construction.  Authorities  differ  con- 
siderably in  the  factors  given  for  heat  losses,  and  there  are  various 
methods  for  computing  the  same.  The  figures  given  in  Table  V  have 
been  used  extensively  in  actual  practice,  and  have  been  found  to  give 
good  results  when  used  with  judgment.  The  table  gives  the  heat  losses 
through  different  thicknesses  of  walls,  doors,  windows,  etc.,  in  B.  T. 
U.,  per  square  foot  of  surface  per  hour,  for  varying  differences  in  inside 
and  outside  temperatures. 

In  computing  the  heat  loss  through  walls,  only  those  exposed  to 
the  outside  air  are  considered. 

In  order  to  make  the  use  of  the  table  clear,  we  shall  give  a  num- 
ber of  examples  illustrating  its  use: 

Example  1.  Assuming  an  inside  temperature  of  70°,  what  will  be  the 
heat  loss  from  a  room  having  an  exposed  wall  surface  of  200  square  feet  and  a 
glass  surface  of  50  square  feet,  when  the  outside  temperature  is  zero?  The 
wall  is  of  brick,  16  inches  in  thickness,  and  has  a  southern  exposure;  the  win- 
dows are  single;  and  the  construction  is  of  the  best,  so  that  no  account  need 
be  taken,  of  leakage 

We  find  from  Table  V,  that  the  factor  for  a  16-inch  brick  wall 
with  a  difference  in  temperature  of  70°  is  19,  and  that  for  glass  (single 
window)  under  the  same  condition  is  85;  therefore, 

Loss  through  walls         =  200  X   19   =  =    3,800 
Loss  through  windows  =       50  X  85   =  =   4,250 

Total  loss  per  hour  -   8,050  B.  T.  U. 

Example  2.  A  room  15  ft.  square  and  10  ft.  high  has  two  exposed  walls, 
one  toward  the  north,  and  the  other  toward  the  west.  There  are  4  windows, 
each  3  feet  by  6  feet  in  size.  The  two  in  the  north  wall  are  double,  while  the 


16  HEATING  AND  VENTILATION 

other  two  are  single.  The  walls  are  of  brick,  20  inches  in  thickness.  With  an 
inside  temperature  of  70°,  what  will  be  the  heat  loss  per  hour  when  it  is  10° 
below  zero? 

Total  exposed  surface  =  15  X  10  X  2  -  300 
Glass  surface  =,3X6X4=     72 

Net  wall  surface     =  228 

Difference  between  inside  and  outside  temperature  80°. 
Factor  for  20-inch  brick  wall  is  18. 
Factor  for  single  window  is  93. 
Factor  for  double  window  is  62. 
The  heat  losses  are  as  follows : 

Wall,  228  X  18  =  4,104 

Single  windows,     36  X  93  =  3,348 

Double  windows,   36  X  62  =  2,232 

9,684  B.T.U. 

As  one  side  is  toward  the  north,  and  the  other  toward  the  west,  the 
actual  exposure  is  N.  W.    Looking  in  Table  VI,  we  find  the  correction 
factor  for  this  exposure  to  be  1.26;  therefore  the  total  heat  loss  is 
9,684  X  1.26  =  12,201.84 B.T.U. 

Example  3.  A  dwelling-house  of  fair  wooden  construction  measures 
160  ft.  around  the  outside;  it  has  2  stories,  each  8  ft.  in  height;  the  windows 
are  single,  and  the  glass  surface  amounts  to  one-fifth  the  total  exposure;  the 
attic  and  cellar  are  unwarmed.  If  8,000  B.  T.  U.  are  utilized  from  each  pound 
of  coal  burned  in  the  furnace,  how  many  pounds  will  be  required  per  hour  to 
maintain  a  temperature  of  70°  when  it  is  20°  above  zero  outside? 

Total  exposure  =     160  X  16  =  2,560 
Glass  surface    =  2,560  -*-    5  =     512 


Net  wall  =2,048 

Temperature  difference  =  70  -  20  =  50° 
Wall          2,048  X  13     =  26,624 
Glass  512  X  60    =  30,720 


57,344  B.T.U. 

As  the  building  is  exposed  on  all  sides,  the  factor  for  exposure  will  be 
the  average  of  those  for  N.,  E.,  S.,  and  W.,  or 

(1.32  +  1.12  +  1.0  +  1.20)  -5-  4  =  1.16 
The  house  has  a  cold  cellar  and  attic,  so  we  must  increase  the  heat  loss 


HEATING  AND  VENTILATION  17 

10  per  cent  for  each  of  the  first  two  conditions,  and  20  per  cent  for  the 
last.     Making  these  corrections  we  have: 

57,344  X  1.16  X  1.10  X  1.10  X  1.20  =  96,338B.T.U. 
If  one  pound  of  coal  furnishes  8,000  B.  T.  IL,  then  96,338  -T-  8,000  = 
12  pounds  of  coal  -per  hour  required  to  warm  the  building  to  70° 
under  the  conditions  stated. 

Approximate  Method.  For  dwelling-houses  of  the  average  con- 
struction, the  following  simple  method  for  calculating  the  heat  loss 
may  be  used.  Multiply  the  total  exposed  surface  by  45,  which  will 
give  the  heat  loss  in  B.  T.  U.  per  hour  for  an  inside  temperature  of  70° 
in  zero  weather. 

This  factor  is  obtained  in  the  following  manner :  Assume  the  glass 
surface  to  be  one-sixth  the  total  exposure,  which  is  an  average  propor- 
tion. Then  each  square  foot  of  exposed  surface  consists  one-sixth 
of  glass  and  five-sixths  of  wall,  and  the  heat  loss  for  70°  difference  in 
temperature  would  be  as  follows : 

Wall  4-  X  19  =  15.8 
6 

Glass  —  X  85  -  14.1 
6  

29.9 

Increasing  this  20  per  cent  for  leakage,  16  per  cent  for  exposure,  and 
10  per  cent  for  cold  ceilings,  we  have : 

29.9  X  1.20  X  1.16  X  1.10  =  45. 

The  loss  through  floors  is  considered  as  being  offset  by  including 
the  kitchen  walls  of  a  dwelling-house,  which  are  warmed  by  the  range, 
and  which  would  not  otherwise  be  included  if  computing  the  size  of  a 
furnace  or  boiler  for  heating. 

If  the  heat  loss  is  required  for  outside  temperatures  other  than 
zero,  multiply  by  50  for  10  degrees  below,  and  by  40  for  10  degrees 
above  zero. 

This  method  is  convenient  for  approximations  in  the  case  of 
dwelling-houses;  but  the  more  exact  method  should  be  used  for  other 
types  of  buildings,  and  in  all  cases  for  computing  the  heating  surface 
for  separate  rooms.  When  calculating  the  heat  loss  from  isolated 
rooms,  the  cold  inside  walls  as  well  as  the  outside  must  be  considered. 

The  loss  through  a  wall  next  to  a  cold  attic  or  other  unwarmed  space 
may  in  general  be  taken  as  about  two-thirds  that  of  an  outside  wall. 


18  HEATING  AND  VENTILATION 

Heat  Loss  by  Ventilation.  One  B.  T.  U.  will  raise  the  tempera- 
ture of  1  cubic  foot  of  air  55  degrees  at  average  temperatures  and 
pressures,  or  will  raise  55  cubic  feet  1  degree,  so  that  the  heat  required 
for  the  ventilation  of  any  room  can  be  found  by  the  following  formula : 

Cu.  ft.  of  air  per  hour  X  Number  of  degrees  rise  =   fi  T  ^    required 
oo 

To  compute  the  heat  loss  for  any  given  room  which  is  to  be 
ventilated,  first  find  the  loss  through  walls  and  windows,  and  correct 
for  exposure  and  leakage;  then  compute  the  amount  required  for 
ventilation  as  above,  and  take  the  sum  of  the  two.  An  inside  tem- 
perature of  70°  is  always  assumed  unless  otherwise  stated. 

Examples.  What  quantity  of  heat  will  be  required  to  warm  100,000 
cubic  feet  of  air  to  70°  for  ventilating  purposes  when  the  outside  temperature 
is  10  below  zero? 

100,000  X  80  -T-  55  =  145,454  B.  T.  U. 

How  many  B.  T.  U.  will  be  required  per  hour  for  the  ventilation  of  a 
church  seating  500  people,  in  zero  weather? 

Referring  to  Table  III,  we  find  that  the  total  air  required  per 
hour  is  1,200  X  500  =  600,000  cu.  ft.;  therefore  600,000  X  70  -*-  55 
=  763,636  B.  T.  U. 

„.  Rise  in  Temperature .  .  „ 

The  factor  -  — — is  approximately  1.1  tor  60  , 

55 

1.3  for  70°,  and  1.5  for  80°.  Assuming  a  temperature  of  70°  for  the 
entering  air,  we  may  multiply  the  air-volume  supplied  for  ventilation 
by  1.1  for  an  outside  temperature  of  10°  above  0,  by  1.3  for  zero,  and 
by  1.5  for  10°  below  zero — which  covers  the  conditions  most  commonly 
met  with  in  practice. 

EXAMPLES  FOR  PRACTICE 

1.  A  room  in  a  grammar  school  28  ft.  by  32  ft.  and  12  feet  high  is 
to  accommodate  50  pupils.     The  walls  are  of  brick  16  inches  in  thick- 
ness; and  there  are  6  single  windows  in  the  room,  each  3  ft.  by  6  ft.; 
there  are  warm  rooms  above  and  below;  the  exposure  is  S.  E.     How 
many  B.  T.  U.  will  be  required  per  hour  for  warming  the  room,  and 
how  many  for  ventilation,  in  zero  weather,  assuming  the  building  to 
be  of  average  construction? 

ANS.      24,261  +  for  warming;  152,727  +  for  ventilation. 

2.  A  stone  church  seating  400  people  has  walls  20  inches  in 
thickness.     It  has  a  wall  exposure  of  5,000  square  feet,  a  glass  expos- 


HEATING  AND  VENTILATION  19 

ure  (single  windows)  of  600  square  feet,  and  a  roof  exposure  of  7,000 
square  feet;  the  roof  is  of  2-inch  pine  plank,  and  the  factor  for  heat 
loss  may  be  taken  the  same  as  for  a  2-inch  wooden  door.  The  floor 
is  of  wood  on  brick  arches,  and  has  an  area  of  4,000  square  feet.  The 
building  is  exposed  on  all  sides,  and  is  of  first-class  construction. 
What  will  be  the  heat  required  per  hour  for  both  warming  and  ventila- 
tion when  the  outside  temperature  is  20°  above  zero? 

ANS.     296,380  for  warming;  436,363  +  for  ventilation. 
3.     A  dwelling-house  of  average  wooden  construction  measures 
200  feet  around  the  outside,  and  has  3  stories,  each  9   feet   high. 
Compute  the  heat  loss  by  the  approximate  method  when  the  tem- 
perature is  10°  below  zero. 

ANS.     270,000  B.  T.  U.  per  hour. 

FURNACE  HEATING 

In  construction,  a  furnace  is  a  large  stove  with  a  combustion 
chamber  of  ample  size  over  the  fire,  the  whole  being  inclosed  in  a 
casing  of  sheet  iron  or  brick.  The  bottom  of  the  casing  is  provided 
with  a  cold-air  inlet,  and  at  the  top  are  pipes  which  connect  with 
registers  placed  in  the  various  rooms  to  be  heated.  Cold,  fresh  air 
is  brought  from  out  of  doors  through  a  pipe  or  duct  called  the  cold-air 
box;  this  air  enters  the  space  between  the  casing  and  the  furnace  near 
the  bottom,  and,  in  passing  over  the  hot  surfaces  of  the  fire-pot  and 
combustion,  chamber,  becomes  heated.  It  then  rises  through  the 
warm-air  pipes  at  the  top  of  the  casing,  and  is  discharged  through  the 
registers  into  the  rooms  above. 

As  the  warm  air  is  taken  from  the  top  of  the  furnace,  cold  air 
flows  in  through  the  cold-air  box  to  take  its  place.  The  air  for  heating 
the  rooms  does  not  enter  the  combustion  chamber. 

Fig.  5  shows  the  general  arrangement  of  a  furnace  with  its  con- 
necting pipes.  The  cold-air  inlet  is  seen  at  the  bottom,  and  the  hot-air 
pipes  at  the -top;  these  are  all  provided  with  dampers  for  shutting  off  or 
regulating  the  amount  of  air  flowing  through  them.  The  feed  or  fire 
door  is  shown  at  the  front,  and  the  ash  door  beneath  it;  a  water-pan  is 
placed  inside  the  casing,  and  furnishes  moisture  to  the  warm  air  before 
passing  into  the  rooms;  water  is  either  poured  into  the  pan  through  an 
opening  in  the  front,  provided  for  this  purpose,  or  is  supplied  auto- 
matically through  a  pipe. 


20 


HEATING  AND  VENTILATION 


The  fire  is  regulated  by  means  of  a  draft  slide  in  the  ash  door,  and 
a  cold-air  or  regulating  damper  placed  in  the  smoke-pipe.  Clean-out 
doors  are  placed  at  different  points  in  the  casing  for  the  removal  of 


ashes  and  soot.    Furnaces  are  made  either  of  cast  iron,  or  of  wrought- 
iron  plates  riveted  together  and  provided  with  brick-lined  firepots. 

Types  of  Furnaces.     Furnaces  may  be  divided  into  two  general 


HEATING  AND  VENTILATION 


21 


types  known  as  direct-draft  and  indirect-draft.  Fig.  6  shows  a  com- 
mon form  of  direct-draft  furnace  with  a  brick  setting;  the  better  class 
have  a  radiator,  generally  placed  at  the  top,  through  which  the  gases 
pass  before  reaching  the  smoke-pipe.  They  have  but  one  damper, 
usually  combined  witK^a  cold-air  check.  Many  of  the  cheaper  direct- 


Fig.  6.    A  Common  Type  of  Direct-Draft  Furnace  in  Brick  Setting. 
Cast-Iron  Radiator  at  Top. 

draft  furnaces  have  no  radiator  at  all,  the  gases  passing  directly  into 
the  smoke-pipe  and  carrying  away  much  heat  that  should  be  utilized. 

The  furnace  shown  in  Fig.  6  is  made  of  cast  iron  and  has  a  large 
radiator  at  the  top;  the  smoke  connection  is  shown  at  the  rear. 

Fig.  7  represents  another  form  of  direct-draft  furnace.  In  this 
case  the  radiator  is  made  of  sheet-steel  plates  riveted  together,  and  the 
outer  casing  is  of  heavy  galvanized  iron  instead  of  brick. 

In  the  ordinary  indirect-draft  type  of  furnace  (see  Fig.  8),  the 
gases  pass  downward  through  flues  to  a  radiator  located  near  the  base, 


22 


HEATING  AND  VENTILATION 


thence  upward  through  another  flue  to  the  smoke-pipe.  In  addition 
to  the  damper  in  the  smoke-pipe,  a  direct-draft  damper  is  required 
to  give  direct  connection  with  the  funnel  when  coal  is  first  put  on,  to 
facilitate  the  escape  of  gas  to  the  chimney.  When  the  chimney  draft 


Fig.  7.    Direct- Draft  Furnace  with  Galvanized-Iron  Casing.    Radiator  (at  top) 
Made  of  Riveted  Steel  Plates. 

is  weak,  trouble  from  gas  is  more  likely  to  be  experienced  with  fur- 
naces of  this  type  than  with  those  having  a  direct  draft. 

Grates.  No  part  of  a  furnace  is  of  more  importance  than  the 
grates.  The  plain  grate  rotating  about  a  center  pin  was  for  a  long 
time  the  one  most  commonly  used.  These  grates  were  usually  pro- 
vided with  a  clinker  door  for  removing  any  refuse  too  large  to  pass 
between  the  grate  bars.  The  action  of  such  grates  tends  to  leave  a 


HEATING  AND  VENTILATION 


23 


cone  of  ashes  in  the  center  of  the  fire  causing  it  to  burn  more  freely 
around  the  edges.  A  better  form  of  grate  is  the  revolving  triangular 
pattern,  which  is  now  used  in  many  of  the  leading  furnaces.  It  con- 
sists of  a  series  of  triangular  bars  having  teeth.  The  bars  are  con- 
nected by  gears,  and  are  turned  by  means  of  a  detachable  lever.  If 


Indirect-Draft  Type  of  Furnace.    Gases  Pass  Downward  to  Radiator  at  Bottom, 
Thence  Upward  to  Smoke-Pipe. 


properly  used,  this  grate  will  cut  a  slice  of  ashes  and  clinkers  from 
under  the  entire  fire  with  little,  if  any  loss  of  unccnsumed  coal. 

The  Firepot.  Firepots  are  generally  made  of  cast  iron  or  of  steel 
plate  lined  with  firebrick.  The  depth  ranges  from  about  12  to  18 
inches.  In  cast-iron  furnaces  of  the  better  class,  the  firepot  is  made 
very  heavy,  to  insure  durability  and  to  render  it  less  likely  to  become 
red-hot.  The  firepot  is  sometimes  made  in  two  pieces,  to  reduce  the 


24  HEATING  AND  VENTILATION 

liability  to  cracking.  The  heating  surface  is  sometimes  increased  by 
corrugations,  pins,  or  ribs. 

A  firebrick  lining  is  necessary  in  a  wrought-iron  or  steel  furnace 
to  protect  the  thin  shell  from  the  intense  heat  of  the  fire.  Since  brick- 
lined  firepots  are  much  less  effective  than  cast-iron  in  transmitting 
heat,  such  furnaces  depend  to  a  great  extent  for  their  efficiency  on  the 
heating  surface  in  the  dome  and  radiator;  and  this,  as  a  rule,  is  much 
greater  than  in  those  of  cast  iron. 

Cast-iron  furnaces  have  "the  advantage  when  coal  is  first  put  on 
(and  the  drop  flues  and  radiator  are  cut  out  by  the  direct  damper)  of 
still  giving  off  heat  from  the  firepot,  while  in  the  case  of  brick  linings 
very  little  heat  is  given  off  in  this  way,  and  the  rooms  are  likely  to 
become  somewhat  cooled  before  the  fresh  coal  becomes  thoroughly 
ignited. 

Combustion  Chamber.  The  body  of  the  furnace  above  the  fire- 
pot,  commonly  called  the  dome  or  feed  section,  provides  a  combustion 
chamber.  This  chamber  should  be  of  sufficient  size  to  permit  the 
gases  to  become  thoroughly  mixed  with  the  air  passing  ap  through  the 
fire  or  entering  through  openings  provided  for  the  purpose  in  the  feed 
door.  In  a  well-designed  furnace,  this  space  should  be  somewhat 
larger  than  the  firepot. 

Radiator.  The  radiator,  so  called,  with  which  all  furnaces  of 
the  better  class  are  provided,  acts  as  a  sort  of  reservoir  in  which  the 
gases  are  kept  in  contact  with  the  air  passing  over  the  furnace  until 
they  have  parted  with  a  considerable  portion  of  their  heat.  Radiators 
are  built  of  cast  iron,  of  steel  plate,  or  of  a  combination  of  the  two. 
The  former  is  more  durable  and  can  be  made  with  fewer  joints,  but 
owing  to  the  difficulty  of  casting  radiators  of  large  size,  steel  plate  is 
commonly  used  for  the  sides. 

The  effectiveness  of  a  radiator  depends  on  its  form,  its  heating 
surface,  and  the  difference  between  the  temperature  of  the  gases  and 
the  surrounding  air.  Owing  to  the  accumulation  of  soot,  the  bottom 
surface  becomes  practically  worthless  after  the  furnace  has  been  in 
use  a  short  time;  surfaces,  to  be  effective,  must  therefore  be  self- 
cleaning. 

If  the  radiator  is  placed  near  the  bottom  of  the  furnace  the  gases 
are  surrounded  by  air  at  the  lowest  temperature,  which  renders  the 
radiator  more  effective  for  a  given  size  than  if  placed  near  the  top  and 


HEATING  AND  VENTILATION  25 

surrounded  by  warm  air.  On  the  other  hand,  the  cold  air  has  a  ten- 
dency to  condense  the  gases,  and  the  acids  thus  formed  are  likely  to 
corrode  the  iron. 

Heating  Surface.  The  different  heating  surfaces  may  be  de- 
scribed as  follows:  I^irepot  surface;  surfaces  acted  upon  by  direct 
rays  of  heat  from  the  fire,  such  as  the  dome  or  combustion  chamber; 
gas-  or  smoke-heated  surfaces,  such  as  flues  or  radiators;  and  ex- 
tended surfaces,  such  as  pins  or  ribs.  Surfaces  unlike  in  character 
and  location,  -vary  greatly  in  heating  power,  so  that,  in  making  com- 
parisons of  different  furnaces,  we  must  know  the  kind,  form,  and 
location  of  the  heating  surfaces,  as  well  as  the  area. 

In  some  furnaces  having  an  unusually  large  amount  of  surface, 
it  will  be  found  on  inspection  that  a  large  part  would  soon  become 
practically  useless  from  the  accumulation  of  soot.  In  others  a  large 
portion  of  the  surface  is  lined  with  firebrick,  or  is  so  situated  that  the 
air-currents  are  not  likely  to  strike  it. 

The  ratio  of  grate  to  heating  surface  varies  somewhat  according 
to  the  size  of  furnace.  It  may  be  taken  as  1  to  25  in  the  smaller  sizes, 
and  1  to  15  in  the  larger. 

Efficiency.  One  of  the  first  items  to  be  determined  in  esti- 
mating the  heating  capacity  of  a  furnace,  is  its  efficiency — that  is, 
the  proportion  of  the  heat  in  the  coal  that  may  be  utilized  for  warming. 
The  efficiency  depends  chiefly  on  the  area  of  the  heating  surface  as 
compared  with  the  grate,  on  its  character  and  arrangement,  and  on 
the  rate  of  combustion.  The  usual  proportions  between  grate  and 
heating  surface  have  been  stated.  The  rate  of  combustion  required 
to  maintain  a  temperature  of  70°  in  the  house,  depends,  of  course, 
on  the  outside  temperature.  In  very  cold  weather  a  rate  of  4  to  5 
pounds  of  coal  per  square  foot  of  grate  per  hour  must  be  main-» 
tained. 

One  pound  of  good  anthracite  coal  will  give  off  about  13,000 
B.  T.  U.,  and  a  good  furnace  should  utilize  70  per  cent  of  this  heat. 
The  efficiency  of  an  ordinary  furnace  is  often  much  less,  sometimes 
as  low  as  50  per  cent. 

In  estimating  the  required  size  of  a  first-class  furnace  with  good 
chimney  draft,  we  may  safely  count  upon  a  maximum  combustion 
of  5  pounds  of  coal  per  square  foot  of  grate  per  hour,  and  may  assume 
that  8,000  B.  T.  U.  will  be  utilized  for  warming  purposes  from  each 


26  HEATING  AND  VENTILATION 

pound  burned.  This  quantity  corresponds  to  an  efficiency  of  60 
per  cent. 

Heating  Capacity.  Having  determined  the  heat  loss  from  a 
building  by  the  methods  previously  given,  it  is  a  simple  matter  to 
compute  the  size  of  grate  necessary  to  burn  a  sufficient  quantity  of 
coal  to  furnish  the  amount  of  heat  required  for  warming. 

In  computing  the  size  of  furnace,  it  is  customary  to  consider  the 
whole  house  as  a  single  room,  with  four  outside  walls  and  a  cold  attic. 
The  heat  losses  by  conduction  and  leakage  are  computed,  and  in- 
creased 10  per  cent  for  the  cold  attic,  and  16  per  cent  for  exposure. 
The  heat  delivered  to  the  various  rooms  may  be  considered  as  being 
made  up  of  two  parts  —  first,  that  required  to  warm  the  outside  air 
up  to  70°  (the  temperature  of  the  rooms);  and  second,  the  quantity 
which  must  be  added  to  this  to  offset  the  loss  by  conduction  and  leak- 
age. Air  is  usually  delivered  through  the  registers  at  a  temperature 
of  120°,  with  zero  conditions  outside,  in  the  best  class  of  residence 

work;  so  that  —  —  of  the  heat  given  to  the  entering  air  may  be  con- 

50 
sidered  as  making  up  the  first  part,  mentioned  above,  leaving 


available  for  purely  heating  purposes.     From  this  it  is  evident  that 

50 
the  heat  supplied  to  the  entering  air  must  be  equal  to  1    -=-  ---     =2.4 

times  that  required  to  offset  the  loss  by  conduction  and  leakage. 

Example.  The  loss  through  the  walls  and  windows  of  a  building  is 
found  to  be  80,000  B.  T.  U.  per  hour  in  zero  weather.  What  will  be  the  size 
of  furnace  required  to  maintain  an  inside  temperature  of  70  degrees? 

From  the  above,  we  have  the  total  heat  required,  equal  to  80,000 
X  2.4  -  192,000  B.  T.  U.  per  hour.  If  we  assume  that  8,000  B.  T. 
U.  are  utilized  per  pound  of  coal,  then  192,000  +  8,000  =  24  pounds 
of  coal  required  per  hour;  and  if  5  pounds  can  be  burned  on  each 

24 

square  foot  of  grate  per  hour,  then  —  =  4.8   square  feet  required. 

o 

A  grate  30  inches  in  diameter  has  an  area  of  4.9  square  feet,  and  is  the 
size  we  should  use. 

When  the  outside  temperature  is  taken  as  10°  below  zero,  multi- 
ply by  2.6  instead  of  2.4;  and  multiply  by  2.8  for  20°  below. 

Table  VII  will  be  found  useful  in  determining  the  diameter  of 
firepot  required. 


HEATING  AND  VENTILATION  27 

TABLE  VII 
Firepot  Dimensions 


AVERAGE  DIAMETER  OF  GRATE,  IN  INCHES 

AREA  IN  SQUARE  FEET 

18       > 

1.77 

20 

2.18 

22 

2.64 

24 

3.14 

26 

3.69 

28 

4.27 

30 

4.91 

32 

5.58 

EXAMPLES   FOR   PRACTICE 

1.  A  brick  apartment  house  is  20  feet  wide,  and  has  4  stories, 
each  being  10  feet  in  height.     The  house  is  one  of  a  block,  and  is 
exposed  only  at  the  front  and  rear.     The  walls  are  16  inches  thick, 
and  the  block  is  so  sheltered  that  no  correction  need  be  made  for 
exposure.     Single  windows  make  up  -J-  the  total  exposed  surface. 
Figure  for  cold  attic  but  warm  basement.     What  area  of  grate  surface 
will  be  required  for  a  furnace  to  keep  the  house  at  a  temperature  of 
70°  when  it  is  10°  below  zero  outside?  ANS.  3.5  square  feet. 

2.  A  house  having  a  furnace  with  a  firepot  30  inches  in  diameter, 
is  not  sufficiently  warmed,  and  it  is  decided  to  add  a  second  furnace 
to  be  used  in  connection  with  the  one  already  in.     The  heat  loss  from 
the  building  is  found  by  computation  to  be  133,600  B.  T.  U.  per  hour, 
in  zero  weather.     What  diameter  of  firepot  will  be  required  for  the 
extra  furnace?  ANS.  24  inches. 

Location  of  Furnace.  A  furnace  should  be  so  placed  that  the 
warm-air  pipes  will  be  of  nearly  the  same  length.  The  air  travels 
most  readily  through  pipes  leading  toward  the  sheltered  side  of  the 
house  and  to  the  upper  rooms.  Therefore  pipes  leading  toward  the 
north  or  west,  or  to  rooms  on  the  first  floor,  should  be  favored  in 
regard  to  length  and  size.  The  furnace  should  be  placed  somewhat 
to  the  north  or  west  of  the  center  of  the  house,  or  toward  the  points 
of  compass  from  which  the  prevailing  winds  blow. 

Smoke=Pipes.  Furnace  smoke-pipes  range  in  size  from  about 
6  inches  in  the  smaller  sizes  to  8  or  9  inches  in  the  larger  ones.  They 
are  generally  made  of  galvanized  iron  of  No.  24  gauge  or  heavier. 
The  pipe  should  be  carried  to  the  chimney  as  directly  as  possible, 


28  HEATING  AND  VENTILATION 

avoiding  bends  which  increase  the  resistance  and  diminish  the  draft. 
Where  a  smoke-pipe  passes  through  a  partition,  it  should  be  pro- 
tected by  a  soapstone  or  double-perforated  metal  collar  having  a 
diameter  at  least  8  inches  greater  than  that  of  the  pipe.  The  top  of 
the  smoke-pipe  should  not  be  placed  within  8  inches  of  unprotected 
beams,  nor  less  than  6  inches  under  beams  protected  by  asbestos  or 
plaster  with  a  metal  shield  beneath.  A  collar  to  make  tight  con- 
nection with  the  chimney  should  be  riveted  to  the  pipe  about  5  inches 
from  the  end,  to  prevent  the  pipe  being  pushed  too  far  into  the  flue. 
Where  the  pipe  is  of  unusual  length,  it  is  well  to  cover  it  to  prevent 
loss  of  heat  and  the  condensation  of  smoke. 

Chimney  Flues.  Chimney  flues,  if  built  of  brick,  should  have 
walls  8  inches  in  thickness,  unless  terra-cotta  linings  are  used,  when 
only  4  inches  of  brickwork  is  required.  Except  in  small  houses 
where  an  8  by  8-inch  flue  may  be  used,  the  nominal  size  of  the  smoke 
flue  should  be  at  least  8  by  12-inches,  to  allow  for  contractions  or  off- 
sets. A  clean-out  door  should  be  placed  at  the  bottom  of  the  flue, 
for  removing  ashes  and  soot.  A  square  flue  cannot  be  reckoned  at 
its  full  area,  as  the  corners  are  of  little  value.  To  avoid  down  drafts, 
the  top  of  the  chimney  must  be  carried  above  the  highest  point  of  the 
roof  unless  provided  with  a  suitable  hood  or  top. 

Cold=Air  Box.  The  cold-air  box  should  be  large  enough  to 
supply  a  volume  of  air  sufficient  to  fill  all  the  hot-air  pipes  at  the  same 
time.  If  the  supply  is  too  small,  the  distribution  is  sure  to  be  unequal, 
and  the  cellar  will  become  overheated  from  lack  of  air  to  carry  away 
the  heat  generated. 

If  a  box  is  made  too  small,  or  is  throttled  down  so  that  the  volume 
of  air  entering  the  furnace  is  not  large  enough  to  fill  all  the  pipes, 
it  will  be  found  that  those  leading  to  the  less  exposed  side  of  the 
house  or  to  the  upper  rooms  will  take  the  entire  supply,  and  that 
additional  air  to  supply  the  deficiency  will  be  drawn  down  through 
registers  in  rooms  less  favorably  situated.  It  is  common  practice 
to  make  the  area  of  the  cold-air  box  three-fourths  the  combined 
area  of  the  hot-air  pipes.  The  inlet  should  be  placed  where  the 
prevailing  cold  winds  will  blow  into  it;  this  is  commonly  on  the  north 
or  west  side  of  the  house.  If  it  is  placed  on  the  side  away  from  the 
wind,  warm  air  from  the  furnace  is  likely  to  be  drawn  out  through 
the  cold-air  box. 


HEATING  AND  VENTILATION 


29 


Whatever  may  be  the  location  of  the  entrance  to  the  cold-air 
box,  changes  in  the  direction  of  the  wind  may  take  place  which  will 
bring  the  inlet  on  the  wrong  side  of  the  house.  To  prevent  the 
possibility  of  such  changes  affecting  the  action  of  the  furnace,  the 
cold-air  box  is  sometimes  extended  through  the  house  and  left  open 
at  both  ends,  with  check-dampers  arranged  to  prevent  back-drafts. 
These  checks  should  be  placed  some  distance  from  the  entrance,  to 
prevent  their  becoming  clogged  with  snow  or  sleet. 

The  cold-air  box  is  generally  made  of  matched  boards;  but 
galvanized  iron  is  much  better;  it  costs  more  than  wood,  but  is  well 
worth  the  extra  expense  on  account  of  tightness,  which  keeps  the  dust 
and  ashes  from  being  drawn  into  the  furnace  casing  to  be  discharged 
through  the  registers  into  the  rooms  above. 

The  cold-air  inlet  should  be  covered  with  galvanized  wire  netting 
with  a  mesh  of  at  least  three-eighths  of  an  inch.  The  frame  to  which 
it  is  attached  should  not 

„        x,  Al_       .  ,  FOR  RETURNING 

be  smaller  than  the  in-  mjL  f AIR TRQM  ABOVE: 

side   dimensions   of    the 

cold-air  box.     A  door  to 

admit  air  from  the  cellar 

to   the    cold-air    box    is 

generally   provided.     As 

a    rule,    air    should    be 

taken   from  this  source, 

only  when   the  house  is 

temporarily    unoccupied 

or  during  high  winds. 

Return  Duct.  In 
some  cases  it  is  desirable 
to  return  air  to  the  fur- 
nace from  the  rooms 
above,  to  be  reheated.  Ducts  for  this  purpose  are  common  in  places 


GOLD  AIR 
/NLET 


Fig  9. 


Common  Method  of  Connecting  Return  Duct  to 
Cold- Air  Box. 


where  the  winter  temperature  is  frequently  below  zero.  Return 
ducts  when  used,  should  be  in  addition  to  the  regular  cold-air  box. 
Fig.  9  shows  a  common  method  of  making  the  connection  between 
the  two.  By  proper  adjustment  of  the  swinging  damper,  the  air  can 
be  taken  either  from  out  of  doors  or  through  the  register  from  the 
room  above.  The  return  register  is  often  placed  in  the  hallway  of 


30 


HEATING  AND  VENTILATION 


a  house,  so  that  it  will  take  the  cold  air  which  rushes  in  when  the 
door  is  opened  and  also  that  which  may  leak  in  around  it  while 
closed.  Check-valves  or  flaps  of  light  gossamer  or  woolen  cloth 
should  be  placed  between  the  cold-air  box  and  the  registers  to  pre- 
vent back-drafts  during  winds. 

The  return  duct  should  not  be  used  too  freely  at  the  expense  of 
outdoor  air,  and  its  use  is  not  recommended  except  during  the  night 
when  air  is  admitted  to  the  sleeping  rooms  through  open  windows. 

Warm=Air  Pipes.  The  required  size  of  the  warm-air  pipe  to 
any  given  room,  depends  on  the  heat  loss  from  the  room  and  on  the 
volume  of  warm  air  required  to  offset  this  loss.  Each  cubic  foot  of 
air  warmed  from  zero  to  120  degrees  brings  into  a  room  2.2  B.  T.  U. 
We  have  already  seen  that  in  zero  weather,  with  the  air  entering  the 

50 
registers  at  120  degrees,  only   rof  the  heat  contained  in  the  air  is 


available  for  offsetting  the  losses  by  radiation  and  conduction,  so  that 

50 
only  2  .  2  X    -------  ==   .  9"  B.  T.  U.  in  each  cubic  foot  of  entering  air  can 

be  utilized  for  warming  purposes.  Therefore,  if  we  divide  the  com- 
puted heat  loss  in  B.  T.  U.  from  a  room,  by  .9,  it  will  give  the  number 
of  cubic  feet  of  air  at  120  degrees  necessary  to  warm  the  room  in  zero 
weather. 

As  the  outside  temperature  becomes  colder,  the  quantity  of  heat 
brought  in  per  cubic  foot  'of  air  increases;  but  the  proportion  avail- 
able for  warming  purposes  becomes  less  at  nearly  the  same  rate,  so 

TABLE  VIII 
Warm=Air  Pipe  Dimensions 


DIAMETER  OF  PIPE, 
IN  INCHES 

AREA 
IN  SQUARE  INCHES 

AREA 
IN  SQUARE  FEET 

6 

28 

.196 

7 

38 

.267 

8 

50 

.349 

9 

64 

.442 

10 

79 

.545 

11 

95 

.660 

12 

113 

.785  ' 

13 

133 

.922 

14 

154 

1.07 

15 

177 

1.23 

16 

201 

1.40 

HEATING  AND  VENTILATION  31 

that  for  all  practical  purposes  we  may  use  the  figure  .9  for  all  usual 
conditions.  In  calculating  the  size  of  pipe  required,  we  may  assume 
maximum  velocities  of  260  and  380  feet  per  minute  for  rooms  on  the 
first  and  second  floors  respectively.  Knowing  the  number  of  cubic 
feet  of  air  per  minute^to  be  delivered,  we  can  divide  it  by  the  velocity, 
which  will  give  us  the  required  area  of  the  pipe  in  square  feet. 

Round  pipes  of  tin  or  galvanized  iron  are  used  for  this  purpose. 
Table  VIII  will  be  found  useful  in  determining  the  required  diameters 
of  pipe  in  inches. 

Example.  The  heat  loss  from  a  room  on  the  second  floor  is  18,000  B. 
T.  U.  per  hour.  What  diameter  of  warm-air  pipe  will  be  required? 

18,000  -r-  .9  =  20,000  =  cubic  feet  of  air  required  per  hour. 
20,000  -r-  60  =  333  per  minute.  Assuming  a  velocity  of  380  feet 
per  minute,  we  have  333  -r-  380  =  .87  square  foot,  which  is  the 
area  of  pipe  required.  Referring  to  Table  VIII,  we  find  this  comes 
between  a  12-inch  and  a  13-inch  pipe,  and  the  larger  size  would 
probably  be  chosen. 

EXAMPLES   FOR    PRACTICE 

1.  A  first-floor  room  has  a  computed  loss  of  27,000  B.  T.  U. 
per  hour  when  it  is  10°  below  zero.     The  air  for  warming  is  to  enter 
through  two  pipes  of  equal  size,  and  at  a  temperature  of  120  degrees. 
What  will  be  the  required  diameter  of  the  pipes? 

ANS.     14  inches. 

2.  If  in  the  above  example  the  room  had  been  on  the  second 
floor,  and  the  air  was  to  be  delivered  through  a  single  pipe,  what 
diameter  would  be  required? 

Axs.     16  inches. 

Since  long  horizontal  runs  of  pipe  increase  the  resistance  and 
loss  of  heat,  they  should  not  in  general  be  over  12  or  14  feet  in  length. 
This  applies  especially  to  pipes  leading  to  rooms  on  the  first  floor, 
or  to  those  on  the  cold  side  of  the  house.  Pipes  of  excessive  length 
should  be  increased  in  size  because  of  the  added  resistance. 

Figs.  10  and  11  show  common  methods  of  running  the  pipes  in 
the  basement.  The  first  gives  the  best  results,  and  should  be  used 
where  the  basement  is  of  sufficient  height  to  allow  it.  A  damper 
should  be  placed  in  each  pipe  near  the  furnace,  for  regulating  the  flow 
of  air  to  the  different  rooms,  or  for  shutting  it  off  entirely  when  desirecj. 


32 


HEATING  AND  VENTILATION 


While  round  pipe  risers  give  the  best  results,  it  is  not  always 
possible  to  provide  a  sufficient  space  for  them,  and  flat  or  oval  pipes 
are  substituted.  When  vertical  pipes  must  be  placed  in  single  par- 
titions, much  better  results  will  be  obtained  if  the  studding  can  be 


Fig.  10.  Fig.  11. 

Common  Methods  of  Running  Hot- Air  Pipes  in  Basement.    Method  Shown  in  Fig.  10 
is  Preferable  where  Feasible. 

made  5  or  6  inches  deep  instead  of  4  as  is  usually  done.  Flues  should 
never  in  any  case  be  made  less  than  3J  inches  in  depth.  Each  room 
should  be  heated  by  a  separate  pipe.  In  some  cases,  however,  it  is 
allowable  to  run  a  single  riser  to  heat  two  unimportant  rooms  on  an 
upper  floor.  A  clear  space  of  at  least  |  inch  should  be  left  between 
the  risers  and  studs,  and  the  latter  should  be  carefully  tinned,  and  the 

TABLE  IX 
Dimensions  of  Oval  Pipes 


DIMENSION  OF  PlPE 

AREA  IN  SQUARE  INCHES 

6  ovaled  to  5  in. 

27 

7 

4  " 

31 

7 

3|  " 

29 

7 

6  " 

38 

8  - 

5  " 

43 

9 

4  " 

45 

9 

6  " 

57 

9 

5  " 

51 

10 

3J  " 

46 

11 

4  " 

58 

12 

3i  " 

55 

10 

6  " 

67 

11 

5  " 

67 

14 

4  " 

76 

15 

3J  " 

73 

12 

6"  " 

85 

12 

5  " 

75 

19 

4  " 

96 

20 

'  3i  " 

100 

HEATING  AND  VENTILATION 


33 


space  between  them  on  both  sides  covered  with  tin,  asbestos,  or  wire 
lath. 

Table  IX  gives  the  capacity  of  oval  pipes.  A  6-inch  pipe  ovaled 
to  5  means  that  a  6-inch  pipe  has  been  flattened  out  to  a  thickness  of 
5  inches,  and  colump  2  gives  the  resulting  area. 

Having  determined  the  size  of  round  pipe  required,  an  equiva- 
lent oval  pipe  can  be  selected  from  the  table  to  suit  the  space  available. 

Registers.  The  registers  which  control  the  supply  of  warm 
air  to  the  rooms,  generally  have  a  net  area  equal  to  two-thirds  of  their 
gross  area.  The  net  area  should  be  from  10  to  20  per  cent  greater 
than  the  area  of  the  pipe  connected  with  it.  It  is  common  practice 
to  use  registers  having  the  short  dimensions  equal  to,  and  the  long 
dimensions  about  one-half  greater  than,  the  diameter  of  the  pipe. 
This  would  give  standard  sizes  for  different  diameters  of  pipe,  as 
listed  in  Table  X. 

TABLE  X 
Sizes  of  Registers  for  Different  Sizes  of  Pipes 


DIAMETER  OF  PIPE 


SIZE  OF  REGISTER 


G  ii 

i. 

6  X  10  i 

n. 

7  ' 

7  X  10  ' 

8  ' 

( 

8  X  12 

9  ' 

t 

9  X  14 

10 

10  X  15 

11 

11  X  16 

12 

12  X  17 

13 

14  X  20 

14 

14  X  22 

15 

15  X  22 

16 

16  X  24 

Combination  Systems.  A  combination  system  for  heating  by 
hot  air  and  hot  water  consists  of  an  ordinary  furnace  with  some  form 
of  surface  for  heating  water,  placed  either  in  contact  with  the  fire  or 
suspended  above  it.  Fig.  12  shows  a  common  arrangement  where 
part  of  the  heating  surface  forms  a  portion  of  the  lining  to  the  firepot 
and  the  remainder  is  above  the  fire. 

Care  must  be  taken  to  proportion  properly  the  work  to  be  done 
by  the  air  and  the  water;  else  one  will  operate  at  the  expense  of  the 
other.  One  square  foot  of  heating  surface  in  contact  with  the  fire  is 
capable  of  supplying  from  40  to  50  square  feet  of  radiating  surface, 


34 


HEATING  AND  VENTILATION 


and  one  square  foot  suspended  over  the  fire  will  supply  from  15  to  25 
square  feet  of  radiation. 

The  value  or  efficiency  of  the  heating  surface  varies  so  widely  in 
different  makes  that  it  is  best  to  state  the  required  conditions  to  the 


Fig.  12.    Combination  Furnace,  for  Heating  by  Both  Hot  Air  and  Hot  Water. 

manufacturers  and  have  them  proportion  the  surfaces  as  their  experi- 
ence has  found  best  for  their  particular  type  of  furnace. 

Care  and  Management  of  Furnaces.  The  following  general 
rules  apply  to  the  management  of  all  hard  coal  furnaces. 

The  fire  should  be  thoroughly  shaken  once  or  twice  daily  in  cold 
weather.  It  is  well  to  keep  the  firepot  heaping  full  at  all  times.  In 


HEATING  AND  VENTILATION  35 


this  way  a  more  even  temperature  may  be  maintained,  less  attention  is 
required,  and  no  more  coal  is  burned  than  when  the  pot  is  only  partly 
filled.  In  mild  weather  the  mistake  is  frequently  made  of  carrying  a 
thin  fire,  which  requires  frequent  attention  and  is  likely  to  die  out. 
Instead,  to  diminish  the  temperature  in  the  house,  keep  the  firepot 
full  and  allow  ashes  xto  accumulate  on  the  grate  (not  under  it)  by  shak- 
ing less  frequently  or  less  vigorously.  The  ashes  will  hold  the  heat 
and  render  it  an  easy  matter  to  maintain  and  control  the  fire.  When 
feeding  coal  on  a  low  fire,  open  the  drafts  and  neither  rake  nor  shake 
the  fire  till  the  fresh  coal  becomes  ignited.  The  air  supply  to  the  fire 
is  of  the  greatest  importance.  An  insufficient  amount  results  in  incom- 
plete combustion  and  a  great  loss  of  heat.  To  secure  proper  combus- 
tion, the  fire  should  be  controlled  principally  by  means  of  the  ash-pit 
through  the  ash-pit  door  or  slide. 

The  smoke-pipe  damper  should  be  opened  only  enough  to  carry 
off  the  gas  or  smokd  and  to  give  the  necessary  draft.  The  openings 
in  the  feed  door  act  as  a  check  on  the  fire,  and  should  be  kept  closed , 
during  cold  weather,  except  just  after  firing,  when  with  a  good  draft 
they  may  be  partly  opened  to  increase  the  air-supply  and  promote  the 
proper  combustion  of  the  gases. 

Keep  the  ash-pit  clear  to  avoid  warping  or  melting  the  grate. 
The  cold-air  box  should  be  kept  wide  open  except  during  winds  or 
when  the  fire  is  low.  At  such  times  it  may  be  partly,  but  never  com- 
pletely closed.  Too  much  stress  cannot  be  laid  on  the  importance 
of  a  sufficient  air-supply  to  the  furnace.  It  costs  little  if  any  more 
to  maintain  a  comfortable  temperature  in  the  house  night  and  day 
than  to  allow  the  rooms  to  become  so  cold  during  the  night  that  the 
fire  must  be  forced  in  the  morning  to  warm  them  up  to  a  comfortable 
temperature. 

In  case  the  warm  air  fails  at  times  to  reach  certain  rooms,  it 
may  be  forced  into  them  by  temporarily  closing  the  registers  in  other 
rooms.  The  current  once  established  will  generally  continue  after 
the  other  registers  have  been  opened. 

It  is  best  to  burn  as  hard  coal  as  the  draft  will  warrant.  Egg 
size  is  better  than  larger  coal,  since  for  a  given  weight  small  lumps 
expose  more  surface  and  ignite  more  quickly  than  larger  ones.  The 
furnace  and  smoke-pipe  should  be  thoroughly  deaned  once  a  year. 


30  HEATING  AND  VENTILATION 

This  should  be  done  just  after  the  fire  has  been  allowed  to  go  out  in 
the  spring. 

STEAM    BOILERS 

Types.  The  boilers  used  for  heating  are  the  same  as  have  already 
been  described  for  power  work.  In  addition  there  is  the  cast-iron 
sectional  boiler,  used  almost  exclusively  for  dwelling-houses. 

Tubular  Boilers.  Tubular  boilers  are  largely  used  for  heating 
purposes,  and  are  adapted  to  all  classes  of  buildings  except  dwelling- 
houses  and  the  special  cases  mentioned  later,  for  which  sectional 
boilers  are  preferable.  A  boiler  horse-power  has  been  defined  as  the 
evaporation  of  34  J  pounds  of  water  from  and  at  a  temperature  of  212 
degrees,  and  in  doing  this  33,317  B.  T.  U.  are  absorbed,  which  are 
again  given  out  when  the  steam  is  condensed  in  the  radiators.  Hence 
to  find  the  boiler  H.  P.  required  for  warming  any  given  building,  we 
have  only  to  compute  the  heat  loss  per  hour  by  the  methods  already 
given,  and  divide  the  result  by  33,330.  It  is  more  common  to  divide 
by  the  number  33,000,  which  gives  a  slightly  larger  boiler  and  is  on 
the  side  of  safety. 

The  commercial  horse-power  of  a  well-designed  boiler  is  based 
upon  its  heating  surface;  and  for  the  best  economy  in  heating  work, 
it  should  be  so  proportioned  as  to  have  about  1  square  foot  heating  of 
surface  for  each  2  pounds  of  water  to  be  evaporated  from  and  at  212 
degrees  F.  This  gives  34.5  -?-  2  =  17.2  square  feet  of  heating  surface 
per  horse-power,  which  is  generally  taken  as  15  in  practice.  Makers  of 
tubular  boilers  commonly  rate  them  on  a  basis  of  12  square  feet  of  heat- 
ing surface  per  horse-power. .  This  is  a  safe  figure  under  the  conditions 
of  power  work,  where  skilled  firemen  are  employed  and  where  more 
care  is  taken  to  keep  the  heating  surfaces  free  from  soot  and  ashes. 
For  heating  plants,  however,  it  is  better  to  rate  the  boilers  upon  15 
square  feet  per  horse-power  as  stated  above. 

There  is  some  difference  of  opinion  as  to  the  proper  method  of 
computing  the  heating  surface  of  tubular  boilers.  In  general,  all 
surface  is  taken  which  is  exposed  to  the  hot  gases  on  one  side  and  to 
the  water  on  the  other.  A  safe  rule,  and  the  one  by  which  Table 
XII  is  computed,  is  to  take  J  the  area  of  the  shell,  f  of  the  rear  head, 
less  the  tube  area,  and  the  interior  surface  of  all  the  tubes. 

The  required  amount  of  grate  area,  and  the  proper  ratio  of  heat- 


HEATING  AND  VENTILATION 


37 


ing  surface  to  grate  area,  vary  a  good  deal,  depending  on  the  character 
of  the  fuel  and  on  the  chimney  draft.  By  assuming  the  probable 
rates  of  combustion  and  evaporation,  we  may  compute  the  required 
grate  area  for  any  boiler  from  the  formula : 

//.  P.  x  34.5 

E  XC        ' 
in  which 

S  =  Total  grate  area,  in  square  feet; 

E  =  Pounds  of  water  evaporated  per  pound  of  coal ; 

C   =  Pounds  of  coal  burned  per  square  foot  of  grate  per  hour. 

Table  XI  gives  the  approximate  grate  area  per  H.  P.  for  different 
rates  of  evaporation  and  combustion  as  computed  by  the  above 
equation. 

TABLE  XI 

Orate   Area  per   Horse-Power  for  Different  Rates  of  Evaporation  and 

Combustion 

i  • 

POUNDS  OF  COAL  BURNED  PER  SQUARE  FOOT  OF  GRATE  PER  HOUR 


POUNDS  OF  STEAM  PER 
POUND  OF  COAL 

8  Ibs; 

10  Ibs. 

12  Ibs. 

Square  Feef  of  Grate  Surface  per  Horse-  Power 

10 

.43 

.35 

.28 

9 

.48 

.38 

.32 

8 

.54 

.43 

.36 

7 

.62 

.49 

.41 

6 

.72 

.58 

.48 

For  example,  with  an  evaporation  of  8  pounds  of  steam  per  pound  of 
coal,  and  a  combustion  of  10  pounds  of  coal  per  square  foot  of  grate,  .43  of  a 
square  foot  of  grate  surface  per  H.  P.  would  be  called  for. 

The  ratio  of  heating  to  grate  surface  in  this  type  of  boiler  ranges 
from  30  to  40,  and  therefore  allows  under  ordinary  conditions  a  com- 
bustion of  from  8  to  10  pounds  of  coal  per  square  foot  of  grate.  This 
is  easily  obtained  with  a  good  chimney  draft  and  careful  firing.  The 
larger  the  boiler,  the  more  important  the  plant  usually,  and  the  greater 
the  care  bestowed  upon  it,  so  that  we  may  generally  count  on  a  higher 
rate  of  combustion  and  a  greater  efficiency  as  the  size  of  the  boiler 
increases.  Table  XII  will  be  found  very  useful  in  determining 
the  size  of  boiler  required  under  different  conditions.  The  grate 
area  is  computed  for  an  evaporation  of  8  pounds  of  water  per  pound 


38 


HEATING  AND  VENTILATION 


TABLE   XII 


DIAMETER 
OF  SHELL 
IN    INCHES 

NUMBER 
OF  TUBES 

DIAMETER 
OF  TUBES 
IN   INCHES 

LENGTH 
OF  TUBES 
IN   FEET 

HORSE- 
POWER 

SIZE   OF 
GRATE  IN 
INCHES 

SIZE  OF 
UPTAKE 
IN  INCHES 

SIZE  OF 
SMOKE- 
PIPE  IN 
SQ.  IN 

30 

28 

^A 

6 

8.5 

24x36 

10x14 

140 

7 

9.9 

24  x  36 

10x14 

140 

8 

11.2 

24  x36 

10  x  14 

140 

9 

12.6 

24  x  42 

10x14 

140 

10 

14.0 

24x42 

10x14 

140 

36 

34 

-Y 

8 

13.6 

30x36 

10x16 

160 

9 

15.3 

30  x  42 

10x18 

180 

10 

16.9 

30  x  42 

10x18 

180 

11 

18.6 

30x48 

10  x  20 

200 

12 

20.9 

30  x  48 

10  x  20 

200 

42 

34 

3 

9 

18.5 

36x42 

10x20 

200 

10 

20.5 

36x42 

10x20 

200 

11 

22.5 

36  x  48 

10x25 

250 

12 

24.5 

36  x  48 

10x25 

250 

13 

26.5 

36  x48 

10x28 

280 

14 

28.5 

36  x  54 

10x28 

280 

48 

44 

3 

10 

30.4 

42x48 

10x28 

280 

11 

33.2 

42  x48 

10x28 

280 

12 

35.7 

42  x  54 

10x32 

320 

. 

13 

38.3 

42x54 

10x32 

320 

14 

40.8 

42x60 

10x36 

360 

15 

43.4 

42  x  60 

10x36 

360 

16 

45.9 

42x60 

10x36 

360 

54 

54 

3 

11 

34.6 

48  x  54 

10x38 

380 

12 

87.7 

48  x  54 

10x38 

380 

13 

40.8 

48  x  54 

10x38 

880 

14 

43.9 

48x54 

10x38 

380 

15 

47.0 

48x60 

10x40 

400 

16 

50.1 

48  x60 

10x40 

400 

46 

»1A 

17 

53.0 

48x60 

10x40 

400 

60 

72 

3 

12 

48.4 

54x60 

12x40 

460 

13 

52.4 

54x60 

12x40 

460 

14 

56.4 

54  x60 

12x40 

460 

15 

60.4 

54x66 

12x42 

500 

16 

64.4 

54x66 

12x42 

500 

64 

Syf, 

17 

71.4 

54  x  72 

12x48 

550 

18 

75.6 

54  x  72 

12x48 

550 

66 

90 

8 

14 

70.1 

60x66 

12x48 

500 

15 

75.0 

60x72 

12x52 

626 

16 

80.0 

60x72 

12x52 

620 

78 

&i/2 

17 

86.0 

60  x  78 

12x56 

670 

18 

91.1 

60x78 

12x56 

670 

19 

96.2 

60  x  78 

12x56 

670 

6*2 

4 

20 

93.1 

60x78 

12x56 

670 

72 

114 

3 

14 

87.4 

66x72 

12x56 

670 

15 

93.6 

66x72 

12x56 

670 

16 

99.7 

66  x78 

12  x  62  . 

740 

98 

3J4 

17 

106.4 

66  x  78 

12x62 

740 

18 

112.6 

66  x84 

12x66 

790 

19 

118.8 

66x84 

12  x66 

790 

72 

4 

20 

107.3 

66x84 

12x66 

790 

HEATING  AND  VENTILATION  39 

of  coal,  which  corresponds  to  an  efficiency  of  about  60  per  cent,  and 
is  about  the  average  obtained  in  practice  for  heating  boilers. 

The  areas  of  uptake  and  smoke-pipe  are  figured  on  a  basis  of 
1  square  foot  to  7  square  feet  of  grate  surface,  and  the  results  given 
in  round  numbers.  'In  the  smaller  sizes  the  relative  size  of  smoke- 
pipe  is  greater.  The  rate  of  combustion  runs  from  6  pounds  in  the 
smaller  sizes  to  11 J  in  the  larger.  Boilers  of  the  proportions  given 
in  the  table,  correspond  well  with  those  used  in  actual  practice,  and 
may  be  relied  upon  to  give  good  results  under  all  ordinary  conditions. 

Water-tube  boilers  are  often  used  for  heating  purposes,  but  more 
especially  in  connection  with  power  plants.  The  method  of  com- 
puting the  required  H.  P.  is  the  same  as  for  tubular  boilers. 

Sectional  Boilers.  Fig.  13  shows  a  common  form  of  cast-iron 
boiler.  It  is  made  up  of  slabs  or  sections,  each  one  of  which  is  con- 
nected by  nipples  with  headers  at  the  sides  and  top.  The  top  header 
acts  as  a  steam  drum,  and  the  lower  ones  act  as  mud  drums ;  they  also 
receive  the  water  of  condensation  from  the  radiators.  The  gases 
from  the  fire  pass  backward  and  forward  through  flues  and  are  finally 
taken  off  at  the  rear  of  the  boiler. 

Another  common  form  of  sectional  boiler  is  shown  in  Fig.  14. 
It  is  made  up  of  sections  which  increase  the  length  like  the  one  just 
described.  These  boilers  have  no  drum  connecting  with  the  sections; 
but  instead,  each  section  connects  with  the  adjacent  one  through 
openings  at  the  top  and  bottom,  as  shown. 

The  ratio  of  heating  to  grate  surface  in  boilers  of  this  type  ranges 
from  15  to  25  in  the  best  makes.  They  are  provided  with  the  usual 
attachments,  such  as  pressure-gauge,  water-glass,  gauge-cocks,  and 
safety-valve ;  a  low-pressure  damper  regulator  is  furnished  for  operat- 
ing the  draft  doors,  thus  keeping  the  steam  pressure  practically  con- 
stant. A  pressure  of  from  1  to  5  pounds  is  usually  carried  on  these 
boilers,  depending  upon  the  outside  temperature.  The  usual  setting 
is  simply  a  covering  of  some  kind  of  non-conducting  material  like 
plastic  magnesia  or  asbestos,  although  some  forms  are  enclosed  in 
light  brickwork. 

In  computing  the  required  size,  we  may  proceed  in  the  same 
manner  as  in  the  case  of  a  furnace.  For  the  best  types  of  house- 
heating  boilers,  we  may  assume  a  combustion  of  5  pounds  of  coal  per 
square  foot  of  grate  per  hour,  and  an  average  efficiency  of  60  per  cent, 


40 


HEATING  AND  VENTILATION 


which  corresponds  to  8,000  B.  T.  U.  per  pound  of  coal,  available  for 
useful  work. 

In  the  case  of  direct-steam  heating,  we  have  only  to  supply  heat 
to  offset  that  lost  by  radiation  and  conduction;  so  that  the  grate  ares 
may  be  found  by  dividing  the  computed  heat  loss  per  hour  by  8,000, 
which  gives  the  number  of  pounds  of  coal;  and  this  in  turn,  divided 
by  5,  will  give  the  area  of  grate  required.  The  most  efficient  rate  of 


Pig.  13.    Common  Type  of  Cast-Iron  Sectional  Boiler.    J*ote  Headers  at  Sides  and  Top 

Acting  as  Drums. 


combustion  will  depend  somewhat  upon  the  ratio  between  the  grate 
and  heating  surface.  It  has  been  found  by  experience  that  about  J 
of  a  pound  of  "coal  per  hour  for  each  square  foot  of  heating  surface 
gives  the  best  results ;  so  that,  by  knowing  the  ratio  of  heating  surface 
to  grate  area  for  any  make  of  heater,  we  can  easily  compute  the  most 
efficient  rate  of  combustion,  and  from  it  determine  the  necessary  grate 


area. 


HEATING  AND  VENTILATION 


41 


For  example,  suppose  the  heat  loss  from  a  building  to  be  480,000 
B.  T.  U.  per  hour,  and  that  we  wish  to  use  a  heater  in  which  the  ratio 
of  heating  surface  to  grate  area  is  24.  What  will  be  the  most  efficient 
rate  of  combustion  and  the  required  ^^^^^ 

grate   area?     480,060   -=-  8,000      =  60 
pounds  of  coal  per  hour,  and  24  -=-  4 
=  6,  which  is  the  best  rate  of   com- 
bustion to  employ;  therefore  60   -T-  6 
=  10,  the  grate  area  required. 

There  are  many  different  designs 
of  cast-iron  boilers  for  low-pressure 
steam  and  hot-water  heating.  In  gen- 
eral, boilers  having  a  drum  connected 
by  nipples  with  each  section  give 
dryer  steam  and  hold  a  steadier  water- 
line  than  the  second  form,  especially 
when  forced  above  their  normal  ca- 
pacity. The  steam,  in  passing  through 
the  openings  between  successive -'sec- 
tions in  order  to  reach  the  outlet, 

is  apt  to  carry  with  it  more  or  less  water,  and  to  choke  the  openings, 
thus  producing  an  uneven  pressure  in  different  parts  of  the  boiler. 

In  the  case  of  hot-water  boilers  this  objection  disappears.- 

In  order  to  adapt  this  type  of  boiler  to  steam  work,  the  opening 
between  the  sections  should  be  of  good  size,  with  an  ample  steam 
space  above  the  water-line;  and  the  nozzles  for  the  discharge  of  steam 
should  be  located  at  frequent  intervals. 


Fig.  14.    Another  Type  of  Sectional 
Boiler.  Here  there  are  no  drums, 
the  sections   being  directly 
connected  through  open- 
ings at  top  and  bottom. 
Courtesy  of  American  Jtadiator  Co. 


EXAMPLES    FOR    PRACTICE 

1.  The  heat  loss  from  a  building  is  240,000  B.  T.  U.  per  hour, 
and  the  ratio  of  heating  to  grate  area  in  the  heater  to  be  used  is  20. 
What  will  be  the  required  grate  area?  Axs.  6  sq.  ft. 

2.  The  heat  loss  from  a  building  is  168,000  B.  T.  U.  per  hour,  and 
the  chimney  draft  is  such  that  not  over  3  pounds  of  coal  per  hour  can 
be  burned  per  square  foot  of  grate.     What  ratio  of  heating  to  grate 
area  will  be  necessary,  and  what  will  be  the  required  grate  area? 

ANS.  Ratio,  12.     Grate  area,  7  sq.  ft, 


42  HEATING  AND  VENTILATION 

Cast-iron  sectional  boilers  are  used  for  dwelling-houses,  small 
schoolhouses,  churches,  etc.,  where  low  pressures  are  carried.  They 
are  increased  in  size  by  adding  more  slabs  or  sections.  After  a  certain 
length  is  reached,  the  rear  sections  become  less  and  less  efficient,  thus 
limiting  the  size  and  power. 

Horse=Power  for  Ventilation.  We  already  know  that  one 
B.  T«U.  will  raise  the  temperature  of  1  cubic  foot  of  air  55  degrees, 
or  it  will  raise  100  cubic  feet  y-J-g-  of  55  degrees,  or  T575F  of  1  degree; 
therefore,  to  raise  100  cubic  feet  1  degree,  it  will  take  1  -r-  y/g-,  or  -y/ 
B.  T.U.;  and  to  raise  100  cubic  feet  through  100  degrees,  it  will  take 
Yff-  X  100  B.  T.  U.  In  other  words,  the  B.  T.  U.  required  to  raise 
any  given  volume  of  air  through  any  number  of  degrees  in  tempera- 
ture, is  equal  to 

Volume  of  air  in  cubic  ft.  X  Degrees  raised 
55 

Example.  How  many  B.  T.  U.  are  required  to  raise  100,000 
cubic  feet  of  air  70  degrees? 

m'<™  X  70  =  127,272  + 
oo 

To  compute  the  H.  P.  required  for  the  ventilation  of  a  building, 
we  multiply  the  total  air-supply,  in  cubic  feet  per  hour,  by  the  number 
of  degrees  through  which  it  is  to  be  raised,  and  divide  the  result  by  55. 
This  gives  the  B.  T.  U.  per  hour,  which,  divided  by  33,000,  will  give 
the  H.  P.  required.  In  using  this  rule,  always  take  the  air-supply  in 
cubic  feet  per  hour. 

EXAMPLES  FOR  PRACTICE 

1.  The  heat  loss  from  a  building  is  1,650,000  B.  T.  U.  per  hour. 
There  is  to  be  an  air-supply  of  1,500,000  cubic  feet  per  hour,  raised 
through  70  degrees.     What  is  the  total  boiler  H.  P.  required? 

ANS.  108. 

2.  A  high  school  has  10  classrooms,  each  occupied  by  50  pupils. 
Air  is  to  be  delivered  to  the  rooms  at  a  temperature  of  70  degrees. 
What  will  be  the  total  H.  P.  required  to  heat  and  ventilate  the  building 
when  it  is  10  degrees  below  zero,  if  the  heat  loss  through  walls  and 
windows  is  1,320,000  B.  T.  U.  per  hour?  ANS.  106  + . 

DIRECT=STEAM  HEATING 

A  system  of  direct-steam  heating  consists  (1)  of  a  furnace  and 


HEATING  AND  VENTILATION 


43 


boiler  for  the  combustion  of  fuel  and  the  generation  of  steam;  (2)  a 
system  of  pipes  for  conveying  the  steam  to  the  radiators  and  for 
returning  the  water  of  condensation  to  the  boiler;  and  (3)  radiators 
or  coils  placed  in  the  rooms  for  diffusing  the  heat. 

Various  types  of  boilers  are  used,  depending  upon  the  size  and 
kind  of  building  to  be  warmed.  Some  form  of  cast-iron  sectional 
boiler  is  commonly  used  for  dwelling-houses,  while  the  tubular  or 
water-tube  boiler  is  more  usually  employed  in  larger  buildings. 
Where  the  boiler  is  used  for  heating  purposes  only,  a  low  steam-pres- 
sure of  from  2  to  10  pounds  is  carried,  and  the  condensation  flows 
back  by  gravity  to  the  boiler,  which  is  placed  below  the  lowest  radiator. 
When,  for  any  reason,  a  higher 
pressure  is  required,  the  steam  for 
the  heating  system  is  made  to 
pass  through  a  reducing  valve, 
and  the  condensation  is  returned 
to  the  boiler  by  means  of  a  pump 
or  return  trap. 

Types  of  Radiating  Surface. 
The  radiation  used  indirect-steam 
heating  is  made  up  of  cast-iron 
radiators  of  various  forms,  pipe 
radiators,  and  circulation  coils. 

Cast=Iron  Radiators.  The 
general  form  of  a  cast-iron  sec- 
tional radiator  is  shown  in  Fig. 
15.  Radiators  of  this  type  are 
made  up  of  sections,  the  number 

depending  upon  the  amount  of  heating  surface  required.  Fig.  16 
shows  an  intermediate  section  of  a  radiator  of  this  type. 
It  is  simply  a  loop  with  inlet  and  outlet  at  the  bottom.  The 
end  sections  are  the  same,  except  that  they  have  legs,  as  shown  in 
Fig.  17.  These  sections  are  connected  at  the  bottom  by  special 
nipples,  so  that  steam  entering  at  the  end  fills  the  bottom  of  the 
radiator,  and,  being  lighter  than  the  air,  rises  through  the  loops  and 
forces  the  air  downward  and  toward  the  farther  end,  where  it  is  dis-. 
charged  through  an  air-valve  placed  about  midway  of  the  last  section. 
There  are  many  different  designs  varying  in  height  and  width,  to 


Fig.  15.     Common  Type  of  Cast-Iron 
Sectional  Radiator. 


44 


HEATING  AND  VENTILATION 


suit  all  conditions.     The  wall  pattern  shown  in  Fig.  18  is  very  con- 
venient when  it  is  desired  to  place  the  radiator  above  the  floor,  as  in 

bathrooms,  etc.;  it  is  also  a  con- 
venient form  to  place  under  the 
windows  of  halls  and  churches 
to  counteract  the  effect  of  cold 
down  drafts.  It  is  adapted  to 
nearly  every  place  where  the  or- 
dinary direct  radiator  can  be 
used,  and  may  be  connected  up 
in  different  ways  to*  meet  the  va- 
rious requirements. 

A  low  and  moderately  shallow 
radiator,  with  ample  space  for  the 
circulation  of  air  between  the 
sections,  is  more  efficient  than  a 
deep  radiator  with  the  sections 
closely  packed  together.  One- 
and  two-column  radiators,  so 
called,  are  preferable  to  three- 
and  four-column,  when  there  is  sufficient  space  to  use  them. 


Fig.  16.  Fig.  17. 

Intermediate  and  End  Sections  of  Radiator 
Shown  in  Fig.  15.     The  end  sections 
(at  right)  have  legs. 


Fig.  18.    Cast-Iron  Sectional  Radiator  of  Wall  Pattern. 

The  standard  height  of  a  radiator  is  36  or  38  inches,  and,  if 
possible,  it  is  better  not  to  exceed  this. 


HEATING  AND  VENTILATION 


45 


For  small  radiators,  it  is  better  practice  to  use  lower  sections  and 
increase  the  length;  this  makes  the  radiator  slightly  more  efficient 
and  gives  a  much  better  appearance. 

To  get  the  best  results  from  wall  radiators,  they  should  be  set 
out  at  least  \\  inches  from  the  wall  to  allow  a  free  circulation  of  air 
back  of  them.  Patterns  having  cross-bars  should  be  placed,  if 
possible,  with  the  bars  in  a  vertical  position,  as  their  efficiency  is 
impaired  somewhat  when  placed  horizontally. 

Pipe  Radiators.  This  type  of  radiator  (see  Fig.  19)  is  made  up  of 
wrought-iron  pipes 
screwed  into  a  cast- 
iron  base.  The 
pipes  are  eithercon- 
nected  in  pairs  at 
the  top  by  return 
bends,  or  each  sep- 
arate tube  has  a 
thin  metal  dia- 
phragm passing  up 
the  center  nearly  to 
the  top.  It  is  nec- 
essary that  a  loop 
be  formed,  else  a 
1  'dead  end"  would 
occur.  This  would 
become  filled  with 
air  and  prevent 
steam  from  enter- 
ing, thus  causing  portions  of  the  radiator  to  remain  cold. 

Circulation  Coils.  These  are  usually  made  up  of  1  or  IJ-inch 
wrought-iron  pipe,  and  may  be  hung  on  the  walls  of  a  room  by  means 
of  hook  plates,  or  suspended  overhead  on  hangers  and  rolls. 

Fig.  20  shows  a  common  form  for  schoolhouse  and  similar  work; 
this  coil  is  usually  made  of  IJ-inch  pipe  screwed  into  headers  or 
branch  tees  at  the  ends,  and  is  hung  on  the  wall  just  below  the  windows. 
This  is  known  as  a  branch  coil.  Fig.  21  shows  a  trombone  coil,  which 
is  commonly  used  when  the  pipes  cannot  turn  a  corner,  and  where 
the  entire  coil  must  be  placed  upon  one  side  of  the  room.  Fig.  22 


Fig.  19.    Wrought-Irou  Pipe  Radiator. 


46 


HEATING  AND  VENTILATION 


is  called  a  miter  coil,  and  is  used  under  the  same  conditions  as  a  trom- 
bone coil  if  there  is  room  for  the  vertical  portion.  This  form  is  not 
so  pleasing  in  appearance  as  either  of  the  other  two,  and  is  found  only 
in  factories  or  shops,  where  looks  are  of  minor  importance. 


Fig.  20.    Common  Form  of  "Branch"  Coil  for  Circulation  of  Direct  Steam. 

Overhead  coils  are  usually  of  the  miter  form,  laid  on  the  side  and 
suspended  about  a  foot  from  the  ceiling;  they  are  less  efficient  than 
when  placed  nearer  the  floor,  as  the  warm  air  stays  at  the  ceiling  and 
the  lower  part  of  the  room  is  likely  to  remain  cold.  They  are  used 


D 


Fig.  21.    "Trombone"  Coil.    Used  where  Entire  Coil  must  be  Placed  on  One  Side  of  Room 

only  when  wall  coils  or  radiators  would  be  in  the  way  of  fixtures,  or 
when  they  wrould  come  below  the  water-line  of  the  boiler  if  placed 
near  the  floor. 

When  steam  is  first  turned  on  a  coil,  it  usually  passes  through  a 


Fig.  22. 


'Miter"  Coil.    Adapted,  like  the  "Trombone,"  Only  to  a  Single  Wall. 
Frequently  Used  in  Factories  and  Shops. 


portion  of  the  pipes  first  and  heats  them  while  the  others  remain  cold 
and  full  of  air.  Therefore  the  coil  must  always  be  made  up  in  such 
a  way  that  each  pipe  shall  have  a  certain  amount  of  spring  and  may 
expand  independently  without  bringing  undue  strains  upon  the  others. 
Circulation  coils  should  incline  about  1  inch  in  20  feet  toward  the 


HEATING  AND  VENTILATION  47 

return  end  in  order  to  secure  proper  drainage  and  quietness  of  opera- 
tion. 

Efficiency  of  Radiators.  The  efficiency  of  a  radiator — that  is, 
the  B.  T.  U.  which  it  gives  off  per  square  foot  of  surface  per  hour — 
depends  upon  the  difference  in  temperature  between  the  steam  in  the 
radiator  and  the  surrounding  air,  the  velocity  of  the  air  over  the 
radiator,  and  the  quality  of  the  surface,  whether  smooth  or  rough. 
In  ordinary  low-pressure  heating,  the  first  condition  is  practically 
constant;  but  the  second  varies  somewhat  with  the  pattern  of  the 
radiator.  An  open  design  which  allows  the  air  to  circulate  freely 
over  the  radiating  surfaces,  is  more  efficient  than  a  closed  pattern, 
and  for  this  reason  a  pipe  coil  is  more  efficient  than  a  radiator. 

In  a  large  number  of  tests  of  cast-iron  and  pipe  radiators,  working 
under  usual  conditions,  the  heat  given  off  per  square  foot  of  surface 
per  hour  for  each  degree  difference  in  temperature  between  the  steam 
and  surrounding  air  was  found  to  average  about  1 . 7  B.  T.  U.  The 
temperature  of  steam  at  3  pounds'  pressure  is  220  degrees,  and  220 — 70 
=  150,  which  may  be  taken  as  the  average  difference  between  the 
temperature  of  the  steam  and  the  air  of  the  room,  in  ordinary  low- 
pressure  work.  Taking  the  above  results,  we  have  150  X  1.7  =  255 
B.  T.  U.  as  the  efficiency  of  an  average  cast-iron  or  pipe  radiator. 
This,  for  convenient  use,  may  be  taken  as  250.  A  circulation  coil 
made  up  of  pipes  from  1  to  2  inches  in  diameter,  will  easily  give  off 
300  B.  T.  U.  under  the  same  conditions;  and  a  cast-iron  wall  radiator 
with  ample  space  back  of  it  should  have  an  efficiency  equal  to  that 
of  a  wall  coil.  While  overhead  coils  have  a  higher  efficiency  than 
cast-iron  radiators,  their  position  near  the  ceiling  reduces  their  effec- 
tiveness, so  that  in  practice  the  efficiency  should  not  be  taken  over 
250  B.  T.  U.  per  hour  at  the  most.  Tabulating  the  above  we  have: 

TABLE   XIII 
Efficiency  of  Radiators,  Coils,  etc. 


TYPE  OF  RADIATING  SURFACE 


RADIATION  PER  SQUARE  FOOT  OF  SURFACE 
PER  HOUR 


Cast-iron  Sectional  and  Pipe  Radiators 
Wall  Radiators 
Ceiling  Coils 
Wall  Coils 


250  B.  T.  U. 

300 

200  to  250 

300  " 


48  HEATING  AND  VENTILATION 

If  the  radiator  is  for  warming  a  room  which  is  to  be  kept  at  a 
temperature  above  or  below  70  degrees,  or  if  the  steam  pressure  is 
greater  than  3  pounds,  the  radiating  surface  may  be  changed  in  the 
same  proportion  as  the  difference  in  temperature  between  the  steam 
and  the  air. 

For  example,  if  a  room  is  to  be  kept  at  a  temperature  of  60°,  the 
efficiency  of  the  radiator  becomes  -ff-§-  X  250  ==  268;  that  is,  the 
efficiency  varies  directly  as  the  difference  in  temperature  between  the 
steam  and  the  air  of  the  room.  It  is  not  customary  to  consider  this 
unless  the  steam  pressure  should  be  raised  to  10  or  15  pounds  or  the 
temperature  of  the  rooms  changed  15  or  20  degrees  from  the  normal. 

From  the  above  it  is  easy  to  compute  the  size  of  radiator  for  any 
given  room.  First  compute  the  heat  loss  per  hour  by  conduction  and 
leakage  in  the  coldest  weather;  then  divide  the  result  by  the  effi- 
ciency of  the  type  of  radiator  to  be  used.  It  is  customary  to  make  the 
radiators  of  such  size  that  they  will  warm  the  rooms  to  70  degrees  in 
the  coldest  weather.  As  the  low-temperature  limit  varies  a  good  deal 
in  different  localities,  even  in  the  same  State,  the  lowest  temperature 
for  which  we  wish  to  provide  must  be  settled  upon  before  any  calcu- 
lations are  made.  In  New  England  and  through  the  Middle  and 
Western  States,  it  is  usual  to  figure  on  warming  a  building  to  70 
degrees  when  the  outside  temperature  is  from  zero  to  10  degrees 
below. 

The  different  makers  of  radiators  publish  in  their  catalogues, 
tables  giving  the  square  feet  of  heating  surface  for  different  styles  and 
heights,  and  these  can  be  used  in  determining  the  number  of  sections 
required  for  all  special  cases. 

If  pipe  coils  are  to  be  used,  it  becomes  necessary  to  reduce  square 
feet  of  heating  surface  to  linear  feet  of  pipe;  this  can  be  done  by  means 
of  the  factors  given  below. 

13  =  linear  ft.  of  1  -in.  pipe 

O     O  _  ff  ii  1  1     *  " 

o  tt  tt        if  •    '        it 

£  —  1^-in. 

1.6  =         "         "2  -in.       " 

The  size  of  radiator  is  made  only  sufficient  to  keep  the  room 
warm  after  it  is  once  heated ;  and  no  allowance  is  made  for  warming 
up\  that  is,  the  heat  given  off  by  the  radiator  is  just  equal  to  that  lost 
through  walls  and  windows.  This  condition  is  offset  in  two  ways — 


HEATING  AND  VENTILATION  49 

first,  when  the  room  is  cold,  the  difference  in  temperature  between 
the  steam  and  the  air  of  the  room  is  greater,  and  the  radiator  is  more 
efficient;  and  second,  the  radiator  is  proportioned  for  the  coldest 
weather,  so  that  for  a  greater  part  of  the  time  it  is  larger  than  neces- 
sary. 

EXAMPLES    FOR   PRACTICE 

1 .  The  heat  loss  from  a  room  is  25,000  B.  T.  U.  per  hour  in 
the  coldest  weather.     What  size  of  direct  radiator  will  be  required? 

ANS.  100  square  feet. 

2.  A  schoolroom  is  to  be  warmed  with  circulation  coils  of  11- 
inch  pipe.     The  heat  loss  is  30,000  B.  T.  U.  per  hour.     What  length 
of  pipe  will  be  required?  ANS.  230  linear  feet. 

Location  of  Radiators.  Radiators  should,  if  possible,  be  placed 
in  the  coldest  part  of  the  room,  as  under  windows  or  near  outside 
doors.  In  living  rooms  it  is  often  desirable  to  keep  the  windows  free, 
in  which  case  the  radiators  may  be  placed  at  one  side.  Circulation 
coils  are  run  along  the  outside  wall^  of  a  room  under  the  windows. 
Sometimes  the  position  of  the  radiators  is  decided  by  the  necessary 
location  of  the  pipe  risers,  so  that  a  certain  amount  of  judgment  must 
be  used  in  each  special  case  as  to  the  best  arrangement  to  suit  all 
requirements. 

Systems  of  Piping.  There  are  three  distinct  systems  of  piping, 
known  as  the  two-pipe  system,  the  one-pipe  relief  system,  and  the  one- 
pipe  circuit  system,  with  various  modifications  of  each  and  combina- 
tions of  the  different  systems. 

Fig.  23  shows  the  arrangement  of  piping  and  radiators  in  the 
two-pipe  system.  The  steam  main  leads  from  the  top  of  the  boiler, 
and  the  branches  are  carried  along  near  the  basement  ceiling.  Risers 
are  taken  from  the  supply  branches,  and  carried  up  to  the  radiators 
on  the  different  floors;  and  return  pipes  are  brought  down  to  the 
return  mains,  which  should  be  placed  near  the  basement  floor  below 
the  water-line  of  the  boiler.  Where  the  building  is  more  than  two 
stories  high,  radiators  in  similar  positions  on  different  floors  are  con- 
nected with  the  same  riser,  which  may  run  to  the  highest  floor;  and  a 
corresponding  return  drop  connecting  with  each  radiator  is  carried 
down  beside  the  riser  to  the  basement.  A  system  in  which  the  main 
horizontal  returns  are  below  the  water-line  of  the  boiler  is  said  to 


50 


HEATING  AND  VENTILATION 


have  a  wet  or  sealed  return.  If  the  returns  are  overhead  and  above  the 
water-line,  it  is  called  a  dry  return.  Where  the  steam  is  exposed  to 
extended  surfaces  of  water,  as  in  overhead  returns,  where  the  con- 
densation partially  fills  the  pipes,  there  is  likely  to  be  cracking  or 
water-hammer,  due  to  the  sudden  condensation  of  the  steam  as  it 
comes  in  contact  with  the  cooler  water.  This  is  especially  noticeable 
when  steam  is  first  turned  into  cold  pipes  and  radiators,  and  the  con- 
densation is  excessive.  When  dry  returns  are  used,  the  pipes  should 
be  large  and  have  a  good  pitch  toward  the  boiler. 

In  the  case  of  sealed  returns,  the  only  contact  between  the  steam 


Fig.  23.    Arrangement  of  Piping  and  Radiators  in  "Two-Pipe"  System. 


and  standing  water  is  in  the  vertical  returns,  where  the  exposed  sur- 
faces are  very  small  (being  equal  to  the  sectional  area  of  the  pipes), 
and  trouble  from  water-hammer  is  practically  done  away  with.  Dry 
returns  should  be  given  an  incline  of  at  least  1  inch  in  10  feet,  while 
for  wet  returns  1  inch  in  20  or  even  40  feet  is  ample.  The  ends  of  all 
steam  mains  and  branches  should  be  dripped  into  the  returns.  If  the 
return  is  sealed,  the  drip  may  be  directly  connected  as  shown  in  Fig. 
24;  but  if  it  is  dry,  the  connection  should  be  provided  with  a  siphon 
loop  as  indicated  in  Fig.  25.  The  loop  becomes  filled  with  water, 
and  prevents  steam  from  flowing  directly  into  the  return.  As  the 


HEATING  AND  VENTILATION 


51 


stea 


Ret-urr* 


condensation  collects  in  the  loop,  it  overflows  into  the  return  pipe  and 
is  carried  away.  The  return  pipes  in  this  case  are  of  course  filled  with 
steam  above  the  water;  but  it  is  steam  which  has  passed  through 
the  radiators  and  their  return  connections,  and  is  therefore  at  a 
slightly  lower  pressure; 
so  that,  if  steam  were  ad- 
mitted directly  from  the 
main,  it  would  tend  to 
hold  back  the  water  in 
more  distant  returns  and 
cause  surging  and  crack- 
ing in  the  pipes.  Some-  Fig.  24.  Drip  frora  steam  Mai^nnected  Directly 
times  the  boiler  is  at  a  ,  to  sealed  Return. 

lower  level  than  the  basement  in  which  the  returns  are  run,  and  it  then 
becomes  necessary  to  establish  a  false  water-line.  This  is  done  by 
making  connections  as  shown  in  Fig.  26. 

It  is  readily  seen  that  the  return  water,  in  order  to  reach  the 
boiler,  must  flow  through  the  trap,  which  raises  the  water-line  or 
seal  to  the  level  shown  by  the  dotted  line.  The  balance  pipe  is  to 
equalize  the  pressure  above  and  below  the  water  in  the  trap,  and 
prevent  siphonic  action,  which  would  tend  to  drain  the  water  out  of 
the  return  mains  after  a  flow  was  once  started. 

The  balance  pipe,  when  possible,  should  be  15  or  20  feet  in 
length,  with  a  throttle-valve  placed  near  its  connection  with  the 

main.  This  valve 
should  be  opened  just 
enough  to  allow  the 
steam-pressure  to  act 
upon  the  air  which  oc- 
cupies the  space  above 
the  water  in  the  trap ; 
but  it  should  not  be 
opened  sufficiently  to 
allow  the  steam  to 
enter  in  large  volume  and  drive  the  air  out.  The  success  of  this 
arrangement  depends  upon  keeping  a  layer  or  cushion  of  cool  air 
next  to  the  surface  of  the  water  in  the  trap,  and  this  is  easily  done 
by  following  the  method  here  described. 


Steam 


Pig.  25.    Use  of  Siphon  in  Connecting  Drip  from  Steam 
Main  to  a  "Dry"  Return. 


52 


HEATING  AND  VENTILATION 


One=Pipe  Relief  System.  In  this  system  of  piping,  the  radiators 
have  but  a  single  connection,  the  steam  flowing  in  and  the  condensa- 
tion draining  out  through  the  same  pipe.  Fig.  27  shows  the  method 
of  running  the  pipes  for  this  system.  The  steam  main,  as  before, 
leads  from  the  top  of  the  boiler,  and  is  carried  to  as  high  a  point  as  the 
basement  ceiling  will  allow;  it  then  slopes  downward  with  a  grade 
of  about  1  inch  in  10  feet,  and  makes  a  circuit  of  the  building  or  a 
portion  of  it. 

Risers  are  taken  from  the  top  and  carried  to  the  radiators  above, 
as  in  the  two-pipe  system;  but  in  this  case,  the  condensation  flows 
back  through  the  same  pipe,  and  drains  into  the  return  main  near  the 

floor  through 
drip  connections 
which  are  made 
at  frequent  in- 
tervals. In  a 
two-story  build- 
ing, the  bottom 
of  each  riser  to 
the  second  floor 
is  dripped;  and 
in  larger  build- 
ings, it  is  cus- 
tomary to  drip 
each  riser  that 
has  more  than 
one  radiator  con- 
nected with  it.  If  the  radiators  are  large  and  at  a  considerable  dis- 
tance from  the  next  riser,  it  is  better  to  make  a  drip  connection  for 
each  radiator.  When  the  return  main  is  overhead,  the  risers  should 
be  dripped  through  siphon  loops;  but  the  ends  of  the  branches 
should  make  direct  connection  with  the  returns.  This  is  the  reverse 
of  the  two-pipe  system.  In  this  case  the  lowest  pressure  is  at  the 
ends  of  the  mains,  so  that  steam  introduced  into  the  returns  at  these 
points  will  cause  no  trouble  in  the  pipes  connecting  between  these  and 
the  boiler. 

If  no  steam  is  allowed  to  enter  the  returns,  a  vacuum  will  be 
formed,  and  there  will  be  no  pressure  to  force  the  water  back  to  the 


Fig.  26.    Connections  Made  to  Establish  "False"  Water-Line 
when  Boiler  is  below  Basement  Level. 


HEATING  AND  VENTILATION 


53 


boiler.     A  check-valve  should  always  be  placed  in  the  main  return 


Fig.  27.    Arrangement  of  Piping  and  Radiators  in  "One-Pipe  Relief"  System. 

near  the  boiler,  to  prevent  the  water  from  flowing  out  in  case  of  a 
vacuum  being  formed  suddenly  in  the  pipes. 


Fig.  28.    Arrangement  of  Piping  and  Radiators  in  "One-Pipe  Circuit"  System. 


There  is  but  little  difference  in  the  cost  of  the  two  systems,  as 
larger  pipes  and  valves  are  required  for  the  single-pipe  method. 


54 


HEATING  AND  VENTILATION 


°^ 


Siphon 
Conr»ectfor\ 


a 


i 


CV\ecU  VcLlve 
Connection^ 


With  radiators  of  medium  size  and  properly  proportioned  connections, 
the  single-pipe  system  in  preferable,  there  being  but  one  valve  to 
operate  and  only  one-half  the  number  of  risers  passing  through  the 
lower  rooms. 

One=Pipe  Circuit  System.  In  this  case,  illustrated  in  Fig.  28,  the 
steam  main  rises  to  the  highest  point  of  the  basement,  as  before;  and 
then,  with  a  considerable  pitch,  makes  an  entire  circuit  of  the  build- 
ing, and  again  connects  with  the  boiler  below  the  water-line.  Single 

risers  are  taken 
from  the  top;  and 
the  condensa- 
tion drains  back 
through  the 
same  pipes,  and 
is  carried  along 
with  the  flow  of 
steam  to  the  ex- 
treme end  of  the 
main,  where  it  is 
returned  to  the 
boiler.  The 
main  is  m  a  d  e 
large,  and  of 
the  same  size 

throughout  its  entire  length.  It  must  be  given  a  good  pitch  to  insure 
satisfactory  results. 

One  objection  to  a  single-pipe  system  is  that  the  steam  and  return 
water  are  flowing  in  opposite  directions,  and  the  risers  must  be  made 
of  extra  large  size  to  prevent  any  interference.  This  is  overcome  in 
large  buildings  by  carrying  a  single  riser  to  the  attic,  large  enough 
to  supply  the  entire  building;  then  branching  and  running  "drops" 
to  the  basement.  In  this  system  the  flow  of  steam  is  downward,  as 
well  as  that  of  water.  This  method  of  piping  may  be  used  with  good 
results  in  two-pipe  systems  as  well.  Care  must  always  be  taken  that 
no  pockets  or  low  points  occur  in  any  of  the  lines  of  pipe;  but  if  for 
any  reason  they  cannot  be  avoided,  they  should  be  carefully  drained. 
A  modification  of  this  system,  adapting  it  to  large  buildings,  is 
shown  in  diagram  in  Fig.  29.  The  riser  shown  in  this  case  is  one  of 


Return 


Sealed  Rel-ur-n 


Fig.  29.    "One-Pipe  Circuit"  System. 
Building. 


Adapted  to  a  Large 


ROCOCO    ORNAMENTAL    THREE    COLUMN    PATTERN    RADIATOR    FOB 
WARMING    BY    HOT    WATER. 

American  Radiator  Company. 


HEATING  AND  VENTILATION 


55 


several,  the  number  depending  upon  the  size  of  the  building;  and 
may  be  supplied  at  either  bottom  or  top  as  most  desirable.  If  steam 
is  supplied  at  the  bottom  of  the  riser,  as  shown  in  the  cut,  all  of  the 
drip  connections  with  the  return  drop,  except  the  upper  one,  should 


Fig.  30.    "Two-Pipe"  Connection  of  Radia- 
tor to  Riser  and  Return. 


Fig.  31.    "Ooe-Pipe"  Connection  of  Radia- 
tor to  Basement  Main. 


be  sealed  with  either  a  siphon  loop  or  a  check-valve,  to  prevent  the 
steam  from  short-circuiting  and  holding  back  the  condensation  in  the 
returns  above.  If  an  overhead  supply  is  used,  the  arrangement 
should  be  the  reverse;  that  is,  all  return  connections  should  be  sealed 
except  the  lowest. 

Sometimes  a  separate  drip  is  carried  down  from  each  set  of 
radiators,  as  shown  on  the  lower  story,  being  connected  with  the 
main  return  below  the  water-line  of  the 
boiler.     In  case  this  is  done,  it  is  well  to 
provide  a  check-valve  in  each  drip  below 
the  water-line. 

In  buildings  of  any  considerable  size, 
it  is  well  to  divide  the  piping  system  into 
sections  by  means  of  valves  placed  in  the 
corresponding  supply  and  return  branches. 
These  are  for  use  in  case  of  a  break  in 
any  part  of  the  system,  so  that  it  will  be 
necessary  to  shut  off  only  a  small  part  of 
the  heating  system  during  repairs.  In  tall  buildings,  it  is  customary 
to  place  valves  at  the  top  and  bottom  of  each  riser,  for  the  same 
purpose. 

Radiator  Connections.    Figs.  30,  31,  and  32  show  the  common 


Fig.  32.    "One-Pipe"  Connection 
of  Radiator  to  Riser. 


56  HEATING  AND  VENTILATION 

methods  of  making  connections  between  supply  pipes  and  radiators. 
Fig.  30  shows  a  two-pipe  connection  with  a  riser;  the  return  is  carried 
down  to  the  main  below.  Fig.  31  shows  a  single-pipe  connection 
with  a  basement  main;  and  Fig.  32,  a  single  connection  with  a  riser. 

Care  must  always  be  taken  to  make  the  horizontal  part  of  the 
piping  between  the  radiator  and  riser  as  short  as  possible,  and  to  give 
it  a  good  pitch  toward  the  riser.  There  are  various  ways  of  making 
these  connections,  especially  suited  to  different  conditions;  but  the 
examples  given  serve  to  show  the  general  principle  to  be  followed. 

Figs.  20,  21,  and  22  show  the  common  methods  of  making  steam 
and  return  connections  with  circulation  coils.  The  position  of  the 
air-valve  is  shown  in  each  case. 

Expansion  of  Pipes.     Cold  steam  pipes  expand  approximately 


Fig.  33.     Elevation  and  Plan  of  Swivel-Joint  to  Counteract  Effects  of  Expansion  and 

Contraction  in  Pipes. 

1  inch  in  each  100  feet  in  length  when,  low-pressure  steam  is  turned 
into  them ;  so  that,  in  laying  out  a  system  of  piping,  we  must  arrange 
it  in  such  a  manner  that  there  will  be  sufficient  "spring"  or  "give"  to 
the  pipes  to  prevent  injurious  strains.  This  is  done  by  means  of  off- 
sets and  bends.  In  the  case  of  larger  pipes  this  simple  method  will 
not  be  sufficient,  and  swivel  or  slip  joints  must  be  used  to  take  up  the 
expansion. 

The  method  of  making  up  a  swivel-joint  is  shown  in  Fig.  33. 
Any  lengthening  of  the  pipe  A  will  be  taken  up  by  slight  turning  or 
swivel  movements  at  the  points  B  and  C.  A  slip-joint  is  shown  in 


HEATING  AND  VENTILATION 


57 


Fig.  34.  The  part  c  slides  inside  the  shell  d,  and  is  made  steam- 
tight  by  a  stuffing-box,  as  shown.  The  pipes  are  connected  at  the 
flanges  .4  and  B. 
When  pipes 
pass  through 


6 


Fig.  34.    "Slip-Joint"  Connection  to  Take  Care  of  Expansion 
and  Contraction  of  Pipes. 


floors  or  parti- 
tions, the  wood- 
work should  be 
protected  by  gal- 
v  a  n  i  z  e  d-i  r  o  n 
sleeves  having  a 

diameter  from  f  to  1  inch  greater  than  the  pipe.    Fig.  35  shows  a 

form  of  adjustable  floor-sleeve 
which  may  be  lengthened  or 
shortened  to  conform  to  the 
thickness  of  floor  or  partition. 
If  plain  sleeves  are  used,  a 
plate  should  be  placed  around 


Fig.  35.    Adjustable  Metal  Sleeve  for  Carrying 
Pipe  through  Floor  or  Partition. 


Fig.  36.    Floor -Plate  Adjusted  to  Plain 

Sleeve  for  Carrying  Pipe  through 

Floor  or  Partition. 


the  pipe  where  it  passes  through  the  floor  or  partition.     These  are 


Fig.  37.    Angle  Valve. 


Fig.  38.    Offset  Valve. 
Valves  for  Radiator  Connections. 


Fig.  39.    Corner  Valve. 


made  in  two  parts  so  that  they  may  be  put  in  place  after  the  pipe  is 
hung.     A  plate  of  this  kind  is  shown  in  Fig.  36. 


58 


HEATING  AND  VENTILATION 


Valves.  The  different  styles  commonly  used  for  radiator  con- 
nections are  shown  in  Figs.  37, 38,  and  39,  and  are  known  as  anylc, 
offset,  and  corner  valves,  respectively.  The  first  is  used  when  the 
radiator  is  at  the  top  of  a  riser  or  when  the  connections  are  like  those 
shown  in  Figs.  30,  31,  and  32$  the  second  is  used  when  the  connection 


Fig.  40.    Indicating  Effect  of  Using  Globe  Valve  on  Horizontal  Steam  Supply 
Pipe  or  Dry  Return. 

between  the  riser  and  radiator  is  above  the  floor;  and  the  third,  when 
the  radiator  has  to  be  set  close  in  the  corner  of  a  room  and  there  is  not 
space  for  the  usual  connection. 

A  globe  valve  should  never  be  used  in  a  horizontal  steam  supply 
or  dry  return.  The  reason  for  this  is  plainly 
shown  in  Fig.  40.  In  order  for  water  to  flow 
through  the  valve,  it  must  rise  to  a  height 
shown  by  the  dotted  line,  which  would  half 
fill  the  pipes,  and  cause  serious  trouble  from 
water-hammer.  The  gate  valve  shown  in 
Fig.  41  does  not  have  this  undesirable  fea- 
ture, as  the  opening  is  on  a  level  with  the 
bottom  of  the  pipe. 


Fig.  41.    Gate  Valve. 


Fig.  42.    Simplest  Form  of  Air- Valve.   Operated  by  Hand. 


Air=Valves.  Valves  of  various  kinds  are  used  for  freeing  the 
radiators  from  air  when  steam  is  turned  on.  Fig.  42  shows  the 
simplest  form,  which  is  operated  by  hand.  Fig.  43  is  a  type  of  auto- 
matic valve,  consisting  of  a  shell,  which  is  attached  to  the  radiator. 
J?  is  a  small  opening  which  may  be  closed  by  the  spindle  (7,  which 


HEATING  AND  VENTILATION 


59 


is  provided  with  a  conical  end.  D  is  a  strip  composed  of  a  layer  of 
iron  or  steel  and  one  of  brass  soldered  or  brazed  together.  The 
action  of  the  valve  is  as  follows : 
wrhen  the  radiator  is  cold  and  filled 
with  air  the  valve  stands  as  shown 
in  the  cut.  When  steam  is  turned 
on,  the  air  is  driven  out  through 
the  opening  B.  As  soon  as  this 
is  expelled  and  steam  strikes  the 
strip  D,  the  two  prongs  spring 
apart  owing  to  the  unequal  ex- 
pansion of  the  two  metals  due  to 
the  heat  of  the  steam.  This 
raises  the  spindle  C,  and  closes 
the  opening  so  that  no  steam  can 
escape.  If  air  should  collect  in 
the  valve,  and  the  metal  strip  twmxmm 

Fig.  43.     Radiator  Automatic  Air- Valve. 


Fg.      .        aaor      uomac       r- av 
Operated  by  Metal  Strip  D,  Consisting 
of  Two  Pieces  of  Metal  of  Unequal 
Expansive  Power. 


become  cool,  it  would  contract, 
and  the  spindle  would  drop  and 
allow  the  air  to  escape  through  B 

as  before.  E  is  an  adjusting  nut.  F  is  a  float  attached  to  the  spindle, 
and  is  supposed,  in  case  of  a  sudden  rush 
of  water  with  the  air,  to  rise  and  close  the 
opening;  this  action,  however,  is  some- 
what uncertain,  especially  if  the  pressure 
of  water  continues  for  some  time. 

There  are  other  types  of  valves  acting 
on  the  same  principle.     The  valve  shown 


Jfi  Nonas:'  No.  I 

ft 


Fig.  44.    Automatic  Air- Valve.    Closed  by  Expansion 
of  a  Piece  of  Vulcanite. 


Fig.  45.     Automatic  Air- Valve. 
Operated  by  Expansion  of 
Drum  C'Due  to  Vaporiza- 
tion of  Alcohol  with 
which  it  is  Partly 
Filled. 


in  Fig.  44  is  closed  by  the  expansion  of  a  piece  of  vulcanite  instead 
of  a  metal  strip,  and  has  no  water  float. 


60 


HEATING  AND  VENTILATION 


The  valve  shown  in  Fig.  45  acts  on  a  somewhat  different  prin- 
ciple. The  float  C  is  made  of  thin  brass,  closed  at  top  and  bottom, 
and  is  partially  filled  with  wood  alcohol.  When  steam  strikes  the 
float,  the  alcohol  is  vaporized,  and  creates  a  pressure  sufficient  to 
bulge  out  the  ends  slightly,  which  raises  the  spindle  and  closes  the 
opening  B. 

Fig.  46  shows  a  form  of  so-called  vacuum  valve.  It  acts  in  a 
similar  manner  to  those  already  described,  but  has  in  addition  a 
ball  check  which  prevents  the  air  from  being 
drawn  into  the  radiator,  should  the  steam  go 
down  and  a  vacuum  be  formed.  If  a  partial 
vacuum  exists  in  the  boiler  and  radiators,  the 
boiling  point,  and  consequently  the  tempera- 
ture of  the  steam,  are  lowered,  and  less  heat  is 
given  off  by  the  radiators.  This  method  of 
operating  a  heating  plant  is  sometimes  advo- 
cated for  spring  and  fall,  when  little  heat  is  re- 
quired, and  when  steam  under  pressure  would 
overheat  the  rooms. 

Pipe  Sizes.  The  proportioning  of  the  steam 
pipes  in  a  heating  plant  is  of  the  greatest  im- 
portance, and  should  be  carefully  worked  out 
by  methods  which  experience  has  proved  to  be 
correct.  There  are  several  ways  of  doing  this; 
but  for  ordinary  conditions,  Tables  XIV,  XV, 
and  XVI  have  given  excellent  results  in  actual  practice.  They 
have  been  computed  from  what  is  known  as  D'Arcy's  formula,  with 
suitable  corrections  made  for  actual  working  conditions.  As  the 
computations  are  somewhat  complicated,  only  the  results  will  be  given 
here,  with  full  directions  for  their  proper  use. 

Table  XIV  gives  the  flow  of  steam  in  pounds  per  minute  for 
pipes  of  different  diameters  and  with  varying  drops  in  pressure  be- 
tween the  supply  and  discharge  ends  of  the  pipe.  These  quantities 
are  for  pipes  IjOO  feet  in  length;  for  other  lengths  the  results  must  be 
corrected  by  the  factors  given  in  Table  XVI.  As  the  length  of  pipe 
increases,  friction  becomes  greater,  and  the  quantity  of  steam  dis- 
charged in  a  given  time  is  diminished. 

Table  XIV  is  computed  on  the  assumption  that  the  drop  in 


Fig.  46.    Vacuum  Valve. 


HEATING  AND  VENTILATION 


61 


TABLE   XIV 

Flow  of  Steam  in  Pipes  of  Various  Sizes,  with  Various  Drops  in  Pres> 
sure  between  Supply  and  Discharge  Ends 

Calculated  for  100-Foot  Lengths  of  Pipe 


0 

» 

DROP  IN  PRESSURE  (POUNDS) 

H 

1A 

H 

1 

1^ 

2 

3 

4 

5 

1 

.44 

.63 

.78 

91 

1.13 

1.31 

1.66 

1.97 

2.26 

1M 

.81 

1.16 

1.43 

1.66 

2.05 

2.39 

3.02 

3.59 

4.12 

i^ 

1.06 

1.89 

2.34 

2.71 

3.36 

3.92 

4.94 

5.88 

6.75 

2 

2.93 

4.17 

5.16 

5.99 

7.43 

8.65 

10.9 

13.0 

14.9 

2y2 

5.29 

7.52 

9.32 

10.8 

13.4 

15.6 

19.7 

23.4 

26.9 

3 

8.61 

12.3 

15.2 

17.6 

21.8 

25.4 

32 

31.8 

43.7 

zy2 

12.9 

18.3 

22.6 

26.3 

32.5 

37.9 

47.8 

56.9 

65.3 

4 

181 

25.7 

31.8 

36.9 

45.8 

53.3 

67.2 

80.1 

91.9 

5 

32.2 

45.7 

56.6 

65.7 

81.3 

94.7 

120 

142 

163 

6 

51.7 

73.3 

90.9 

106 

131 

152 

192 

229 

262 

7 

76.7 

109 

135 

157 

194 

226 

285 

339 

390 

8 

108 

154 

190 

222 

274 

319 

402 

478 

549 

9 

147 

209 

258 

299 

371 

432 

545 

649 

745 

10 

192 

273 

339 

393 

487 

567 

715 

852 

977 

12 

305 

434 

537 

623 

771 

899 

1,130 

1,350 

1,550 

15 

535 

761 

942 

1,090 

1,350 

1,580 

1,990 

2,370 

2,720 

pressure  between  the  two  ends  of 'the  pipe  equals  the  initial  pressure. 
If  the  drop  in  pressure  is  less  than  the  initial  pressure,  the  actual 
discharge  will  be  slightly  greater  than  the  quantities  given  in  the  table; 

TABLE   XV 

Factors  for  Calculating  Flow  of  Steam   in  Pipes  under   Initial    Pres- 
sures above  Five  Pounds 

To  be  used  in  connection  with  Table  XIV 


DROP  IN 

INITIAL,  PRESSURE  (POUNDS) 

PRESSURE 

IN  POUNDS 

10 

20 

30 

40 

60 

80 

\ 

1.27 

1.49 

1.68 

1.84 

2.13 

2.38 

! 

1.26 

1.48 

1.66 

1.83 

2.11 

2.36 

1.24 

1.46 

1.64 

1.80 

2.08 

2.32 

2 

1.21 

1.41 

1.59 

1.75 

2.02 

2.26 

3 

1.17 

1.37 

1.55 

1.70 

1.97 

2.20 

4 

1.14 

1.34 

1.51 

1.66 

1  ,92 

2.14 

5 

1.12 

1.31 

1.47 

1.62 

1.87 

2.09 

but  this  difference  will  be  small  for  pressures  up  to  5  pounds,  and  may 
be  neglected,  as  it  is  on  the  side  of  safety.  For  higher  initial  pressures, 
Table  XV  has  been  prepared.  This  is  to  be  used  in  connection  with 
Table  XIV  as  follows:  First  find  from  Table  XIV  the  quantity  of 
steam  which  will  be  discharged  through  the  given  diameter  of  pipe 


62 


HEATING  AND  VENTILATION 


TABLE   XVI 

Factors    for  Calculating  Flow  of    Steam  in    Pipes  of    Other  Lengths 

than    100   Feet 


FEET 

FACTOR 

FEET 

FACTOR 

FEET 

FACTPR 

FEET 

FACTOR 

10 

3.16 

120 

.91 

275  ' 

.60 

600 

.40 

20 

2.24 

130 

.87 

300 

.57 

650 

.39 

30 

1.82 

140 

.84 

325 

.55 

700 

.37 

40 

1.58 

150 

.81 

350 

.53 

750 

.36 

50 

1.41 

160 

.79 

375 

.51 

800 

.35 

60 

1.29 

170 

.76 

400 

.50 

850 

.34 

70 

1.20 

180 

.74 

425 

.48 

900 

.33 

80 

1.12 

190 

.72 

450 

.47 

950 

.32 

90 

1.05 

200 

.70 

475 

.46 

1,000 

.31 

100 

1.00 

225 

.66 

500 

.45 

110 

.95 

250 

.63 

550 

.42 

with  the  assumed  drop  in  pressure;  then  look  in  Table  XV  for  the 
factor  corresponding  with  the  assumed  drop  and  the  higher  initial 
pressure  to  be  used.  The  quantity  given  in  Table  XIV,  multiplied 
by  this  factor,  will  give  the  actual  capacity  of  the  pipe  under  the  given 
conditions. 

Example — What  weight  of  steam  will  be  discharged  through  a  3-inch 
pipe  100  feet  long,  with  an  initial  pressure  of  60  pounds  and  a  drop  of  2  pounds? 

Looking  in  Table  XIV,  we  find  that  a  3-inch  pipe  will  dis- 
charge 25 . 4  pounds  of  steam  per  minute  with  a  2-pound  drop.  Then 
looking  in  Table  XV,  we  find  the  factor  corresponding  to  60  pounds 
initial  pressure  and  a  drop  of  2  pounds  to  be  2.02.  Then  according 
to  the  rule  given,  25.4  X  2.02  =  51. 3  pounds,  which  is  the  capacity 
of  a  3-inch  pipe  under  the  assumed  conditions. 

Sometimes  the  problem  will  be  presented  in  the  following  way: 
What  size  of  pipe  will  be  required  to  deliver  80  pounds  of  steam  a 
distance  of  100  feet  with  an  initial  pressure  of  40  pounds  and  a  drop 
of  3  pounds? 

We  have  seen  that  the  higher  the  initial  pressure  with  a  given 
drop,  the  greater  will  be  the  quantity  of  steam  discharged ;  therefore 
a  smaller  pipe  will  be  required  to  deliver  80  pounds  of  steam  at  40 
pounds  than  at  3  pounds  initial  pressure  From  Table  XV,  we  find 
that  a  given  pipe  will  discharge  1 . 7  times  as  much  steam  per  minute 
with  a  pressure  of  40  pounds  and  a  drop  of  3  pounds,  as  it  would  with 
a  pressure  of  3  pounds,  dropping  to  zero.  From  this  it  is  evident 
that  if  we  divide  80  by  1 .7  and  look  in  Table  XIV  under  "3  pounds 


ivc.r*oii    i   m 
Of  J 

ALFOR^X 


HEATING  AND  VENTILATION  63 

drop"  for  the  result  thus  obtained,  the  size  of  pipe  corresponding  will 
be  that  required.  Now,  80  -f-  1 .7  =  47.  The  nearest  number  in  the 
table  marked  "3  pounds  drop"  is  47.8,  which  corresponds  to  a  3J- 
inch  pipe,  which  i%  the  size  required. 

These  conditions  will  seldom  be  met  with  in  low-pressure  heating, 
but  apply  more  particularly  to  combination  power  and  heating  plants, 
and  will  be  taken  up  more  fully  under  that  head.  For  lengths  of 
pipe  other  than  100  feet,  multiply  the  quantities  given  in  Table  XIV 
by  the  factors  found  in  Table  XVI. 

Example — What  weight  of  steam  will  be  discharged  per  minute  through 
a  3^-inch  pipe  450  feet  long,  with  a  pressure  of  5  pounds  and  a  drop  of  J  pound? 

Table  XIV,  which  may  be  used  for  all  pressures  below  10  pounds, 
gives  for  a  3J-inch  pipe  100  feet  long,  a  capacity  of  18.3  pounds  for 
the  above  conditions.  Looking  in  Table  XVI,  we  find  the  correction 
factor  for  450  feet  to  be  .47.  Then  18.3  X  .47  =  8.6  pounds,  the 
quantity  of  steam  which  will  be  discharged  if  the  pipe  is  450  feet 
long. 

Examples  involving  the  use  of  Tables  XIV,  XV,  and  XVI  in 
combination,  are  quite  common  in  practice.  The  following  example 
will  show  the  method  of  calculation: 

What  size  of  pipe  will  be  required  to  deliver  90  pounds  of  steam  per 
minute  a  distance  of  800  feet,  with  an  initial  pressure  of  80  pounds  and  a  drop 
of  5  pounds? 

Table  XVI  gives  the  factor  for  800  feet  as  .35,  and  Table  XV, 
that  for  80  pounds  pressure  and  5  pounds  drop,  as  2.09.  Then 

90 
— —  =  123,  which    is  the  equivalent  quantity  we  must  look 

.  oo  /\  iL .  uy 

for  in  Table  XIV.  We  find  that  a  4-inch  pipe  will  discharge  91.9 
pounds,  and  a  5-inch  pipe  163  pounds.  A  4^-inch  pipe  is  not  com- 
monly carried  in  stock,  and  we  should  probably  use  a  5-inch  in  this 
case,  unless  it  was  decided  to  use  a  4-inch  and  allow  a  slightly  greater 
drop  in  pressure.  In  ordinary  heating  work,  with  pressures  varying 
from  2  to  5  pounds,  a  drop  of  J  pound  in  100  feet  has  been  found  to 
give  satisfactory  results. 

In  computing  the  pipe  sizes  for  a  heating  system  by  the  above 
methods,  it  would  be  a  long  process  to  work  out  the  size  of  each 
branch  separately.  Accordingly  Table  XVII  has  been  prepared  for 
ready  use  in  low-pressure  work. 


64 


HEATING  AND  VENTILATION 


As  most  direct  heating  systems,  and  especially  those  in  school- 
houses,  are  made  up  of  both  radiators  and  circulation  coils,  an  effi- 
ciency of  300  B.  T.  U.  has  been  taken  for  direct  radiation  of  whatever 
variety,  no  distinction  being  made  between  the  different  kinds.  This 
gives  a  slightly  larger  pipe  than  is  necessary  for  cast-iron  radiators; 
but  it  is  probably  offset  by  bends  in  the  pipes,  and  in  any  case  gives  a 
slight  factor  of  safety.  We  find  from  a  steam  table  that  the  latent 
heat  of  steam  at  20  pounds  above  a  vacuum  (which  corresponds  to 
5  pounds' gauge-pressure)  is  954  +  B.  T.  U. — which  means  that,  for 
every  pound  of  steam  condensed  in  a  "radiator,  954  B.  T.  U.  are  given 
off  for  warming  the  air  of  the  room.  If  a  radiator  has  an  efficiency 
of  300  B.  T.  U.,  then  each  square  foot  of  surface  will  condense  300  -r- 
954  =  .314  pound  of  steam  per  hour;  so  that  we  may  assume  in 
round  numbers  a  condensation  of  J  of  a  pound  of  steam  per  hour  for 
each  square  foot  of  direct  radiation,  when  computing  the  sizes,  of 
steam  pipes  in  low-pressure  heating.  Table  XVII  has  been  calculated 
on  this  assumption,  and  gives  the  square  feet  of  heating  surface 

TABLE  XVII 

Heating  Surface  Supplied  by  Pipes  of  Various  Sizes 
Length  of  Pipe,  100  Feet 


SQUARE  FEET  OP  HEATING  SURFACE 

C!,—  „    ,..,    T>¥ti.r. 

i  Pound  Drop 

\  Pound  Drop 

1 

80 

114 

it 

145 
190 

210 
340 

2 

525 

750 

2* 

950 

1,350 

3 

1,550 

2,210 

3* 

2,320 

3,290 

4 

3,250 

4,620 

5 

5,800 

8,220 

6 

9,320 

13,200 

7 

13,800 

19,620 

8 

19,440 

27,720 

which  different- sizes  of  pipe  will  supply,  with  drops  in  pressure  of 
\  and  \  pounds  in  each  100  feet  of  pipe.  The  former  should  be  used 
for  pressures  from  1  to  5  pounds,  and  the  latter  may  be  used  for 
pressures  over  5  pounds,  under  ordinary  conditions.  The  sizes  of 
long  mains  and  special  pipes  of  large  size  should  be  proportioned 
directly  from  Tables  XIV,  XV,  and  XVI. 


HEATING  AND  VENTILATION 


Where  the  two-pipe  system  is  used  and  the  radiators  have  sepa- 
rate supply  and  return  pipes,  the  risers  or  vertical  pipes  may  be  taken 
from  Table  XVII;  but  if  the  single-pipe  system  is  used,  the  risers 
must  be  increased  jn  size,  as  the  steam  and  water  are  flowing  in  oppo- 
site directions  and 'must  have  plenty  of  room  to  pass  each  other.  It 
is  customary  in  this  case  to  base  the  computation  on  the  velocity  of 
the  steam  in  the  pipes,  rather  than  on  the  drop  in  pressure.  Assum- 
ing, as  before,  a  condensation  of  one-third  of  a  pound  of  steam  per 
hour  per  square  foot  of  radiation,  Tables  XVIII  and  XIX  have  been 
prepared  for  velocities  of  10  and  15  feet  per  second.  The  sizes  given 
in  Table  XIX  have  been  found  sufficient  in  most  cases;  but  the  larger 
sizes,  based  on  a  flow  of  10  feet  per  second,  give  greater  safety  and 
should  be  more  generally  used.  The  size  of  the  largest  riser  should 
usually  be  limited  to  2J  inches  in  school  and  dwelling-house  work, 
unless  it  is  a  special  pipe  carried  up  in  a  concealed  position.  If  the 
length  of  riser  is  short  between  the  lowest  radiator  and  the  main,  a 
higher  velocity  of  20  feet  or  more  may  be  allowed  through  this  por- 
tion, rather  than  make  the  pipe  excessively  large. 

TABLE  XVIII  TABLE  XIX 

Radiating  Surface  Supplied  by  Steam  Risers 


10  FEET  PER  Si 

,COND  VELOCITY 

15  FEET  PER  Si 

:COND  VELOCITY 

Size  of  Pipe 

Sq.  Feet  of  Radiation 

Size  of  Pipe 

Sq.  Feet  of  Radiation 

1     in. 

30 

1      n. 

50 

H 

60 

H 

90 

1* 

80 

H 

120 

2 

130 

2 

200 

2* 

190 

2* 

290 

3 

290 

3 

340 

3* 

390 

3* 

590 

EXAMPLES   FOR  PRACTICE 

1.  How  many  pounds  of  steam  will  be  delivered  per  minute, 
through  a  3J-inch  pipe  600  feet  long,  with  an  initial  pressure  of  5 
pounds  and  a  drop  of  \  pound?  ANS.  7.32  pounds. 

2.  What  size  pipe  will  be  required  to  deliver  25.52  pounds 
of  steam  per  minute  with  an  initial  pressure  of  3  pounds  and  a  drop 
of  \  pound,  the  length  of  the  pipe  being  50  feet?        ANS.  4-inch. 

3.  Compute  the  size  of  pipe  required  to  supply  10,000  square 
feet  of  direct  radiation  (assume  J  of  a  pound  of  steam  per  square 


66 


HEATING  AND  VENTILATION 


foot  per  hour)  where  the  distance  to  the  boiler  house  is  300  feet,  and 
the  pressure  carried  is  10  pounds,  allowing  a  drop  in  pressure  of 
4  pounds.  ANS.  5-inch  (this  is  slightly  larger  than  is  required,  while 
a  4-inch  is  much  too  small). 

TABLE  XX 
Sizes  of  Returns  for  Steam  Pipes  (in  Inches) 


DIAMETER  OF  STEAM  PIPE 

DIAMETER  OF  DRY  RETURN 

DIAMETER  OF  SEALED  RETURN 

1 

1 

i 

11 

1 

li 

H 

i 

2" 

H 

U 

2* 

2" 

H 

3 

2J      . 

2 

3* 

2 

4 

3 

2* 

5 

3 

2* 

6 

3*. 

3 

7 

3i 

3 

8 

4 

3* 

9 

5 

3* 

10 

5 

4 

12 

6 

5 

Returns.  The  size  of  return  pipes  is  usually  a  matter  of  custom 
and  judgment  rather  than  computation.  It  is  a  common  rule  among 
steamfitters  to  make  the  returns  one  size  smaller  than  the  corre- 
sponding steam  pipes.  This  is  a  good  rule  for  the  smaller  sizes,  but 
gives  a  larger  return  than  is  necessary  for  the  larger  sizes  of  pipe. 
Table  XX  gives  different  sizes  of  steam  pipes  with  the  corresponding 
diameters  for  dry  and  sealed  returns. 

TABLE  XXI 
Pipe  Sizes  for  Radiator  Connections 


SQUARE  FEET  OF  RADIATION 

STEAM 

RETURN 

10  to    30 

f  inch 

f  inch 

Two-Pipe 

30  to    48 
48  to    96 

1 

a.     « 

•I               1C 

96  to  150 

H     " 

n  " 

» 

10  to    24 

1    inch 

Single-Pipe 

24  to    60 
60  to    80 

11     " 
H     " 

. 

80  to  130 

2       " 

HEATING  AND  VENTILATIQN 


The  length  of  run  and  number  of  turns  in  a  return  pipe  should 
be  noted,  and  any  unusual  conditions  provided  for.  Where  the 
condensation  is  discharged  through  a  trap  into  a  lower  pressure,  the 
sizes  given  may  be^  slightly  reduced,  especially  among  the  larger 
sizes,  depending  upon  the  differences  in  pressure. 

Radiators  are  usually  tapped  for  pipe  connections  as  shown  in 
Table  XXI,  and  these  sizes  may  be 
used  for  the  connections  with  the 
mains  or  risers. 

Boiler  Connections.  The  steam 
main  should  be  connected  to  the 
rear  nozzle,  if  a  tubular  boiler  is 
used,  as  the  boiling  of  the  water  is 
less  violent  at  this  point  and  dryer 
steam  will  be  obtained.  The  shut- 
off  valve  should  be  placed  in  such  a  position  that  pockets  for  the 
accumulation  of  condensation  will  be  avoided.  Fig.  47  shows  a  good 
position  for  the  valve. 

The  size  of  steam  connection  may  be  computed  by  means  of  the 
methods  already  given,  if  desired.  But  for  convenience  the  sizes 
given  in  Table  XXII  may  be  used  with  satisfactory  results  for  the 
short  runs  between  the  boilers  and  main  header. 

TABLE  XXII 
Pipe  Sizes  from  Boiler  to  Main  Header 


Fig  47.    Good  Position  for  Shut-Off 
Valve. 


DIAMETER  OP  BOILER 


SIZE  OF  STEAM  PIPE 


36  inches 

3  inches 

42 

4 

48 

4 

54 

5 

60 

5 

66 

6 

72   " 

6 

The  return  connection  is  made  through  the  blow-off  pipe,  and 
should  be  arranged  so  that  the  boiler  can  be  blown  off  without  draining 
the  returns.  A  check-valve  should  be  placed  in  the  main  return,  and 
a  plug-cock  in  the  blow-off  pipe.  Fig.  48  shows  in  plan  a  good 
arrangement  for  these  connections. 


HEATING  AND  VENTILATION 


The  ,feed  connections,  with  the  exception  of  that  part  exposed 
in  the  smoke-bonnet,  are  always  made  of  brass  in  the  best. class  of 
work.  The  small  section  referred  to  should  be  of  extra  heavy  wrought 


4//4AV     RETURN 


TO  DRAIN   OR 


^  Fig.  48.    A  Good  Arrangement  of  Return  and  Blow-Off  Connections. 

iron.  The  branch  to  each  boiler  should  be  provided  with  a  gate 
or  globe  valve  and  a  check-valve,  the  former  being  placed  next  to  the 
boiler. 

Table  XXIII  gives  suitable  sizes  for  return,  blow-off,  and  feed 
pipes  for  boilers  of  different  diameters. 

TABLE  XXIII 
Sizes  for  Return,  Blow-Off,  and  Feed  Pipes 


DIAMETER  OF  BOILER 

SIZE  OF  PIPE 
FOR  GRAVITY  RETURN 

SIZE  OF  BLOW-OFF 
PIPE 

SIZE  OF  FEED  PIPE 

36  inches 

1^  inches 

\\  inches 

1     inch 

42 

2 

H       ' 

1 

48 

2 

1* 

1 

54 

2* 

2 

H 

60 

2i 

2 

H 

66 

3 

2*      ' 

1* 

72 

3 

2*      ' 

U 

Blow=0ff  Tank.  Where  the  blow-off  pipe  connects  with  a 
sewer,  some  means  must  be  provided  for  cooling  the  water,  or  the 
expansion  and  contraction  caused  by  the  hot  water  flowing  through 
the  drain-pipes  will  start  the  joints  and  cause  leaks.  For  this  reason 
it  is  customary  to  pass  the  water  through  a  blow-off  tank.  A  form 
of  wrought-iron  tank  is  shown  in  Fig.  49.  It  consists  of  a  receiver 
supported  on  cast-iron  cradles.  The  tank  ordinarily  stands  nearly 
full  of  cold  water. 

The  pipe  from  the  boiler  enters  above  the  water-line,  and  the 
sewer  connection  leads  from  near  the  bottom,  as  shown.  A  vapor 
pipe  is  carried  from  the  top  of  the  tank  above  the  roof  of  the  building. 
When  water  from  the  boiler  is  blown  into  the  tank,  cold  water  from 


HEATING  AND  VENTILATION 


69 


the  bottom  flows  into  the  sewer,  and  the  steam  is  carried  off  through 
the  vapor  pipe.  The  equalizing  pipe  is  to  prevent  any  siphon  action 
which  might  draw  the  water  out  of  the  tank  after  a  flow  is  once  started. 
As  only  a  part  of  the  water  is  blown  out  of  a  boiler  at  one  time,  the 
blow-off  tank  can  be'-of  a  comparatively  small  size.  A  tank  24  by  48 
inches  should  be  large  enough  for  boilers  up  to  48  inches  in  diameter; 


Fig.  49.    Connections  of  Blow-Off  Tank. 

and  one  36  by  72  inches  should  care  for  a  boiler  72  inches  in  diameter. 
If  smaller  quantities  of  water  are  blown  off  at  one  time,  smaller  tanks 
can  be  used.  The  sizes  given  above  are  sufficient  for  batteries  of  2  or 
more  boilers,  as  one  boiler  can  be  blown  off  and  the  water  allowed  to 
cool  before  a  second  one  is  blown  off.  Cast-iron  tanks  are  often 
used  in  place  of  wrought-iron,  and  these  may  be  sunk  in  the  ground 
if  desired. 


'... 


Cast  Iron  Seamless  Tubular  Steam  Heater. 


HEATING  AND  VENTILATION 


PART  II 


INDIRECT  STEAM  HEATING 

As  already  stated,  in  the  indirect  method  of  steam  heating,  a 
special  form  of  heater  is  placed  beneath  the  floor,  and  encased  in 
galvanized  iron  or  in  brickwork:  A  cold-air  box  is  connected  with 
the  space  beneath  the  heater;  and  warm-air  pipes  at  the'  top  are 
connected  with  registers  in  the  floors  or  walls  as  already  described  for 
furnaces.  A  separate  heater  may  be  provided  for  each  register  if  the 
rooms  are  large,  or  two  or  more  registers  may  be  connected  with  the 
same  heater  if  the  horizontal  runs  of  pipe  are  short.  Fig.  50  shows 
a  section  through  a  heater  arranged  for  introducing  hot  air  into  a 
room  through  a  floor  register;  and -Fig.  51  shows  the  same  type  of 
heater  connected  with  a  wall  register.  The  cold-air  box  is  seen  at 
the  bottom  of  the  casing;  and  the  air,  in  passing  through  the  spaces 
between  the  sections  of  the  heater,  becomes  warmed,  and  rises  to  the 
rooms  above. 

Different  forms  of  indirect  heaters  are  shown  in  Figs.  52  and  53. 
Several  sections  con- 
nected in  a  single  group 
are  called  a  stack.  Some- 
times the  stacks  are  en- 
cased in  brickwork  built 
up  from  the  basement 
floor,  instead  of  in  gal- 
vanized iron  as  shown  in 
the  cuts.  This  method 
of  heating  provides  fresh 
air  for  ventilation,  and  for 
this  reason  is  especially 

adapted  for  schoolhouses,  hospitals,  churches,  etc.  As  com- 
pared with  furnace  heating,  it  has  the  advantage  of  being  less 
affected  by  outside  wind-pressure,  as  long  runs  of  horizontal  pipe 


Fig.  50.    Steam  Heater  Placed  under  Floor  Register 
•—Indirect  System. 


72 


HEATING  AND  VENTILATION 


are  avoided  and  the  heaters  can  be  placed  near  the  registers.     In  a 
large  building  where  several  furnaces  would  be  required,  a  single 

boiler  can  be  used,  and  the  num- 
ber of  stacks  increased  to  suit 
the  existing  conditions,  thus 
making  it  necessary  to  run  but 
a  single  fire.  Another  advan- 
tage is  the  large  ratio  between 
the  heating  and  grate  surface 
as  compared  with  a  furnace; 
and  as  a  result,  a  large  quan- 
tity of  air  is  warmed  to  a  mod- 
erate temperature,  in  place  of 
a  smaller  quantity  heated  to  a 
much  higher  temperature. 
This  gives  a  more  agreeable 
quality  to  the  air,  and  renders 
it  less  dry.  Direct  and  indi- 
rect systems  are  often  com- 
bined, thus  providing  the  liv- 
ing rooms  with  ventilation,  while  the  hallways,  corridors,  etc.,  have 
only  direct  radiators  for  warming. 

Types  of  Heaters.  Various  forms  of  indirect  radiators  are  shown 
in  Figs.  52,  53,  54,  and  56.  A  hot-water  radiator  may  be  used  for 
steam;  but  a  steam  radiator  cannot  always  be  used  for  hot  water,  as 


Fig.  51.    Steam  Heater  Connected  to  Wall  Reg- 
ister.—Indirect  System. 


Fig.  52.    One  Form  of  Indirect  Steam  or  Hot- Water  Heater. 

it  must  be  especially  designed  to  produce  a  continuous  flow  of  water 
through  it  from  top  to  bottom.  Figs.  54  and  55  show  the  outside 
and  the  interior  construction  of  a  common  pattern  of  indirect  radiator 


HEATING  AND  VENTILATION 


73 


designed  especially  for  steam.  The  arrows  in  Fig.  55  indicate  the 
path  of  the  steam  through  the  radiator,  which  is  supplied  at  the  right, 
while  the  return  connection  is  at  the  left.  The  air-valve  in  this  case 
should  be  connected  in  the  end  of  the  last  section  near  the  return. 


Fig.  53.    Another  Form  of  Indirect  Steam  or  Hot •  Water  Heater. 

A  very  efficient  form  of  radiator,  and  one  that  is  especially  adapted 
to  the  warming  of  large  volumes  of  air,  as  in  schoolhouse  work,  is 
shown  in  Fig.  56,  and  is  known  as  the  School  pin  radiator.  This  can 


Fig.  54.    Exterior  View  of  a  Common  Type  of  Radiator  for  Indirect-Steam  Heating. 

be  used  for  either  steam  or  hot  water,  as  there  is  a  continuous  passage 
downward  from  the  supply  connection  at  the  top  to  the  return  at  the 
bottom.  These  sections  or  slabs  are  made  up  in  stacks  after  the 


Fig.  55.    Interior  Mechanism  of  Radiator  Shown  in  Fig.  54. 

manner  shown  in  Fig.  57,  which  represents  an  end  view  of  several 
sections  connected  together  with  special  nipples. 

A  very  efficient  form  of  indirect  heater  may  be  made  up  of 
wrought-iron  pipe  joined  together  with  branch  tees  and  return  bends. 


74 


HEATING  ANP  VENTILATION 


A  heater  like  that  shown  in  Fig.  58  is  known  as  a  box  coil.  Its  effi- 
ciency is  increased  if  the  pipes  are  staggered — that  is,  if  the  pipes  in 
alternate  rows  are  placed  over  the  spaces  between  those  in  the  row 
below. 

Efficiency  of    Heaters.    The  efficiency  of   an  indirect   heater 


Fig.  56.    "School  Pin"  Radiator,  Especially  Adapted  for  Warming  Large  Volumes  of 
Air  by  Either  Steam  or  Hot  Water. 

depends  upon  its  form,  the  difference  in  temperature  between  the 
steam  and  the  surrounding  air,  and  the  velocity  with  which  the  air 
passes  over  the  heater.  Under  ordinary  conditions  in  dwelling-house 
work,  a  good  form  of  indirect  radiator  will  give  off  about  2  B.  T.  U. 
per  square  foot  per  hour  for 
each  degree  difference  in  tem- 
perature between  the  .steam 
and  the  entering  air.  Assum- 
ing a  steam  pressure  of  2 
pounds  and  an  outside  tem- 
perature of  zero,  we  should 
have  a  difference  in  tempera- 
ture of  about  220  degrees, 
which,  under  the  conditions 
stated,  would  give  an  efficiency 
of  220  X  2  =  440  B.  T.  U. 
per  hour  for  each  square  foot 
of  radiation.  By  making  a  similar  computation  for  10  degrees  be- 
low zero,  we  find  the  efficiency  to  be  460.  In  the  same  manner  we 
may  calculate  the  efficiency  for  varying  conditions  of  steam  pressure 
and  outside  temperature..  In  the  case  of  schoolhouses  and  similar 
buildings  where  large  volumes  of  air  are  warmed  to  a  moderate  tern- 


Fig.  57.    End  View  of  Several  "School  Pin' 
Radiator  Sections  Connected  Together. 


HEATING  AND  VENTILATION 


75 


perature,  a  somewhat  higher  efficiency  is  obtained,  owing  to  the  in- 
creased velocity  of  the  air  over  the  heaters.  Where  efficiencies  of  440 
and  460  are  used  for  dwellings,  we  may  substitute  600  and  620  for 
schoolhoiises.  This  corresponds  approximately  to  2.7  B.  T.  U.  per 
square  foot  per  hour  for  a  difference  of  1  degree  between  the  air  and 
steam. 

The  principles  involved  in  indirect  steam  heating  are  similar 
to  those  already  described  in  furnace  heating.  Part  of  the  heat  given 
off  by  the  radiator  must  be  used  in  warming  up  the  air-supply  to  the 
temperature  of  the  room,  and  part  for  offsetting  the  loss  by  conduction 
through  walls  and  windows.  The  method  of  computing  the  heating 
surface  required,  depends  upon  the  volume  of  air  to  be  supplied  to  the 
room.  In  the  case  of  a  schoolroom  or  hall,  where  the  air  quantity 


**•  A .    .      ^ 


Fig.  58.    "Box  Coil,"  Built  Up  of  Wrought-Iron  Pipe,  for  Indirect- Steam  Heating. 

is  large  as  compared  with  the  exposed  wall  and  window  surface,  we 
should  proceed  as  follows: 

First  compute  the  B.  T.  U.  required  for  loss  by  conduction 
through  walls  and  windows;  and  to  this,  add  the  B.  T.  U.  required 
for  the  necessary  ventilation;  and  divide  the  sum  by  the  efficiency 
of  the  radiators.  An  example  will  make  this  clear. 

Example.  How  many  square  feet  of  indirect  radiation  will  be  required 
to  warm  and  ventilate  a  schoolroom  in  zero  weather,  where  the  heat  loss  by 
conduction  through  walls  and  windows  is  36,000  B.  T.  U.,  and  the  air-supply 
is  100,000  cubic  feet  per  hour? 

By  the  methods  given  under  "Heat  for  Ventilation/'  we  have 
100,000  X  70  x  127,272  -  B.  T.  U.  required  for  ventilation. 
36,000  +  127,272  =  163,272  B.  T.  U.  =  Total  heat  required. 
This  in  turn  divided  by  600  (the  efficiency  of  indirect  radiators 
under  these  conditions)  gives  272  square  feet  of  surface  required. 


76  HEATING  AND  VENTILATION 

In  the  case  of  a  dwelling-house  the  conditions  are  somewhat 
changed,  for  a  room  having  a  comparatively  large  exposure  will  have 
perhaps  only  2  or  3  occupants,  so  that,  if  the  small  air-quantity  neces- 
sary in  this  case  were  used  to  convey  the  required  amount  or  heat 
to  the  room,  it  would  have  to  be  raised  to  an  excessively  high  temper- 
ature. It  has  been  found  by  experience  that  the  radiating  surface 
necessary  for  indirect  heating  is  about  50  per  cent  greater  than  that 
required  for  direct  heating.  So  for  this  work  we  may  compute  the 
surface  required  for  direct  radiation,  and  multiply  the  result  by  1.5. 

Buildings  like  hospitals  are  in  a  class  between  dwellings  and 
schoolhouses.  The  air-supply  is  based  on  the  number  of  occupants, 
as  in  schools,  but  other  conditions  conform  more  nearly  to  dwelling- 
houses. 

To  obtain  the  radiating  surface  for  buildings  of  this  class,  we 
compute  the  total  heat  required  for  warming  and  ventilation  as  in 
the  case  of  schoolhouses,  and  divide  the  sum  by  the  efficiencies  given 
for  dwellings — that  is,  440  for  zero  weather,  and  460  for  10  degrees 
below. 

Example.  A  hospital  ward  requires  50,000  cubic  feet  of  air  per  hour  for 
ventilation;  and  the  heat  loss  by  conduction  through  walls,  etc.,  is  100,000 
B.  T.  U.  per  hour.  How  many  square  feet  of  indirect  radiation  will  be  required 
to  warm  the  ward  in  zero  weather? 

50,000  X  70  ^  55  =  63,636  B.  T.  U.  for  ventilation;   then, 

63,636  +  100,000 
— - — — —         -  =  372  +  square  feet. 

EXAMPLES  FOR  PRACTICE 

1.  A  schoolroom  having  40  pupils  is  to  be  warmed  and  venti- 
lated when  it  is  10  degrees  below  zero.     If  the  heat  loss  by  conduction 
is  30,000  B.  T.  U.  per  hour,  and  the  air  supply  is  to  be  40  cubic  feet 
per  minute  per  pupil,  how  many  square  feet  of  indirect  radiation  will 
be  required?  ANS.  273. 

2.  A  contagious  ward  in  a  hospital  has  10  beds,  requiring  6,000 
cubic  feet  of  air  each,  per  hour.     The  heat  loss  by  conduction  in  zero 
weather  is  80,000  B.  T.  U.     How  many  square  feet  of  indirect  radia- 
tion will  be  required?  ANS.  355. 

3.  The  heat  loss  from  a  sitting  room  is  11,250  B.  T.  U.  per 
hour  in  zero  weather.     How  many  square  feet  of  indirect  radiation 
will  be  required  to  warm  it?  ANS.  75. 


HEATING  AND  VENTILATION 


77 


IRON 


HE "AT •£•/? 


Stacks  and  Casings.  It  has  already  been  stated  that  a  group  of 
sections  connected  together  is  called  a  stack,  and  examples  of  these 
with  their  casings  are  shown  in  Figs.  50  and  51.  The  casings  are 
usually  made  of  galvanized  iron,  and  are  made  up  in  sections  by 
means  of  small  bo*ks  so  that  they  may  be  taken  apart  in  case  it  is 
necessary  to  make  repairs.  Large  stacks  are  often  enclosed  in  brick- 
work, the  sides  consisting  of  8-inch  walls,  and  the  top  being  covered 
over  with  a  layer  of  brick  and  mortar  supported  on  light  wrought-iron 
tee-bars.  Blocks  of  asbestos  are  sometimes  used  for  covering,  instead 
of  brick,  the  whole  being  covered  over  with  plastic  material  of  the 
same  kind. 

Where  a  single  stack  supplies  several  flues  or  registers,  the 
connections  between  these  and  the  warm-air  chamber  are  made  in 
the  same  manner  as  already  described  for  furnace  heating.  When 
galvanized-iron  casings  are  used,  the  heater  is  supported  by  hangers 
from  the  floor  above.  Fig. 
59  shows  the  method  of 
hanging  a  heater  from  a 
wooden  floor.  If  the  floor 
is  of  fireproof  construc- 
tion, the  hangers  may  pass 

,          u    +u      K     L  WRO'T  IRON  PIPE 

Up     through    the      briCK-    Fig  59     Method  of  Hanging  a  Heater  below  a  Wooden 

work,  and   the   ends    be 

provided  with  nuts  and  large  washers  or  plates ;  or  they  may  be  clamped 
to  the  iron  beams  which  carry  the  floor.  Where  brick  casings  are 
used,  the  heaters  are  supported  upon  pieces  of  pipe  or  light  I-beams 
built  into  the  walls. 

The  warm-air  space  above  the  heater  should  never  be  less  than 
8  inches,  while  12  inches  is  preferable  for  heaters  of  large  size.  The 
cold-air  space  may  be  an  inch  or  two  less;  but  if  there  is  plenty  of 
room,  it  is  good  practice  to  make  it  the  same  as  the  space  above. 

Dampers.  The  general  arrangement  of  a  galvanized-iron  casing 
and  mixing  damper  is  shown  in  Fig.  60.  The  cold-air  duct  is  brought 
along  the  basement  ceiling  from  the  inlet  window,  and  connects 
with  the  cold-air  chamber  beneath  the  heater.  The  entering  air  passes 
up  between  the  sections,  and  rises  through  the  register  above,  as  shown 
by  the  arrows.  When  the  mixing  damper  is  in  its  lowest  position, 
all  air  reaching  the  register  must  pass  through  the  heater;  but  if  the 


nnnnnmn 


78 


HEATING  AND  VENTILATION 


damper  is  raised  to  the  position  shown,  part  of  the  air  will  pass  by 
without  going  through  the  heater,  and  the  mixture  entering  through 
the  register  will  be  at  a  lower  temperature  than  before.  By  changing 


FLOOR 


COLD  A/R 


M/X/MG 


v* 


/HE  AT  > 

r« 

213 

GALVAN/ZED  IRON      SLI&/NG  DOOR 
CAS/NG 

Fig.  60.    General  Arrangement  of  a  Galvanized-Iron  Casing  and  Mixing  Damper. 
Damper  between  Heater  and  Register. 

the  position  of  the  damper,  the  proportions  of  warm  and  cold  air 
delivered  to  the  room  can  be  varied,  thus  regulating  the  temperature 
without  diminishing  to  any  great  extent  the  quantity  of  air  delivered. 


Fig.  61.    Heater  and  Mixing  Damper  with  Brick  Casing.    Damper  between 
Heater  and  Register. 

The  objection  to  this  form  of  damper  is  that  there  is  a  tendency  for 
the  air  to  enter  the  room  before  it  is  thoroughly  mixed;  that  is,  a 
stream  of  warm  air  will  rise  through  one  half  of  the  register  while 


HEATING  AND  VENTILATION 


79 


cold  air  enters  through  the  other.  This  is  especially  true  if  the  con- 
nection between  the  damper  and  register  is  short.  Fig.  61  shows 
a  similar  heater  and  mixing  damper,  with  brick  casing.  Cold  air  is 
admitted  to  the  large  chamber  below  the  heater,  and  rises  through 
the  sections  to  the^register  as  before.  The  action  of  the  mixing 
damper  is  the  same  as  already  described.  Several  flues  or  registers 
may  be  connected  with  a  stack  of  this  form,  each  connection  having, 
in  addition  to  its  mixing  damper,  an  adjusting  damper  for  regulating 
the  flow  of  air  to  the  different  rooms. 

Another  way  of  proportioning  the  air-flow  in  cases  of  this  kind 
is  to  divide  the  hot-air  chamber  above  the  heater  into  sections,  by 
means  of  galvanized-iron  partitions,  giving  to  each  room  its  proper 
share  of  heating  surface.  If  the  cold-air  supply  is  made  sufficiently 
large,  this  arrangement  is  preferable  to  using  adjusting  dampers  as 


•J 

7 

> 

# 

^ 

Fig.  62. 


Another  Arrangement  of  Mixing  Damper  and  Heater  in  Galvanized-Iron 
Casing.    Heater  between  Damper  and  Register. 


described  above.  The  partitions  should  be  carried  down  the  full 
depth  of  the  heater  between  the  sections,  to  secure  the  best  results. 
The  arrangement  shown  in  Fig.  62  is  somewhat  different,  and 
overcomes  the  objection  noted  in  connection  with  Fig.  60,  by  sub- 
stituting another.  The  mixing  damper  in  this  case  is  placed  at  the 
other  end  of  the  heater.  When  it  is  in  its  highest  position,  all  of  the 
air  must  pass  through  the  heater  before  reaching  the  register;  but 
when  partially  lowered,  a  part  of  the  air  passes  over  the  heater, 
and  the  result  is  a  mixture  of  cold  and  warm  air,  in  proportions 
depending  upon  the  position  of  the  damper.  As  the  layer  of  warm 
air  in  this  case  is  below  the  cold  air,  it  tends  to  rise  through  it,  and  a 
more  thorough  mixture  is  obtained  than  is  possible  with  the  damper 
shown  in  Fig.  60.  One  quite  serious  objection,  however,  to  this  form 
of  damper,  is  illustrated  in  Fig.  63.  When  the  damper  is  nearly 


80 


HEATING  AND  VENTILATION 


Fig.  63.    Showing  Difficulty  of  Regulat- 
ing Temperature  with  Arrangement 
in  Fig.  62. 


closed  so  that  the  greater  part  of  the  air  enters  above  the  heater,  it 
has  a  tendency  to  fall  between  the  sections,  as  shown  by  the  arrows, 
and,  becoming  heated,  rises  again,  so  that  it  is  impossible  to  deliver 

air  to  a  room  below  a  certain  tem- 
perature. This  peculiar  action  in- 
creases as  the  quantity  of  air  admit- 
ted below  the  heater  is  diminished. 
When  the  inlet  register  is  placed  in 
the  wall  ai  some  distance  above 
the  floor,  as  in  schoolhouse  work,  a  thorough  mixture  of  air  can  be 
obtained  by  plac- 
ing the  heater  so 
that  the  current 
of  warm  air  will 
pass  up  the  front 
of  the  flue  and  be 
discharged  into 
the  room  through 
the  lower  part  of 
the  register.  This 
is  shown  quite 
clearly  in  Fig.  64, 
where  the  cur- 
rent of  warm  air 
is  represented  by 
crooked  arrows, 
and  the  cold  air 
by  straight  ar- 
rows. The  two 
currents  pass  up 
the  flue  separate- 
ly; but  as  soon 
as  they  are  dis- 
charged through 

Fig.  64.    Arrangement  of  Heater  and  Damper  Causing  Warm  Air 
the    register     the  to  Enter  Room  through  Lower  Part  of  Register,  thus 

Securing  Thorough  Mixing 

warm  air  tends 

to  rise,  and  the  cold  air  to  fall,  with  the  result  of  a  more  or  less 

complete  mixture,  as  shown. 


HEATING  AND  VENTILATION 


81 


It  is  often  desirable  to  warm  a  room  at  times  when  ventilation 
is  not  necessary,  as  in  the  case  of  living  rooms  during  the  night,  or 
for  quick  warming  in  the  morning.  A  register  and  damper  for  air 
rotation  should  be  provided  Li  this  case.  Fig.  65  shows  an  arrange- 
ment for  this  purpose.  When  the  damper  is  in  the  position  shown, 
air  will  be  taken  from  the  room  above  and  be  warmed  over  and  over; 
but,  by  raising  the  damper,  the  supply  will  be  taken  from  outsjde. 
Special  care  should  be  taken  to  make  all  mixing  dampers  tight  against 
air-leakage,  else  their  advantages  will  be  lost.  They  should  work 
easily  and  close  tightly  against  flanges  covered  with  felt.  They  may 
be  operated  from  the  rooms  above  by  means  of  chains  passing  over 


COLD 


SUCT 


\ 


Fig.  65.    Arrangement  for  Quick  Heating  without  Ventilation.    Damper  Shuts  off  Fresh 
Air,  and  Air  of  Room  Heated  by  Rotating  Forth  and  Back  through 
Register  and  Heater. 

guide-pulleys;  special  attachments  should  be  provided  for  holding 
in  any  desired  position. 

Warm=Air  Flues.  The  required  size  of  the  warm-air  flue  between 
the  heater  and  the  register,  depends  first  upon  the  difference  in  tem- 
perature between  the  air  in  the  flue  and  that  of  the  room,  and  second, 
upon  the  height  of  the  flue.  In  dwelling-houses,  where  the  con- 
ditions are  practically  constant,  it  is  customary  to  allow  2  square 
inches  area  for  each  square  foot  of  radiation  when  the  room  is  on  the 
first  floor,  and  1J  square  inches  for  the  second  and  third  floors.  In 
the  case  of  hospitals,  where  a  greater  volume  of  air  is  required,  these 
figures  may  be  increased  to  3  square  inches  for  the  first  floor  wards, 
and  2  square  inches  for  those  on  the  upper  floors. 

In  schoolhouse  work,  it  is  more  usual  to  calculate  the  size  of 
flue  from  an  assumed  velocity  of  air-flow  through  it.  This  will  vary 
greatly  according  to  the  outside  temperature  and  the  prevailing  wind 
conditions.  The  following  figures  may  be  taken  as  average  velocities 


82  HEATING  AND  VENTILATION 

obtained  in  practice,  and  may  be  used  as  a  basis  for  calculating  the 
required  flue  areas  for  the  different  stories  of  a  school  building : 

1st  floor,  280  feet  per  minute. 
2nd     "  ,  340     "       " 
3rd     "  ,  400     " 

These  velocities  will  be  increased  somewhat  in  cold  and  windy  weather 
and  will  be  reduced  when  the  atmosphere  is  mild  and  damp. 

Having  assumed  these  velocities,  and  knowing  the  number  of 
cubic  feet  of  air  to  be  delivered  to  the  room  per  minute,  we  have  only 
to  divide  this  quanity  by  the  assumed  velocity,  to  obtain  the  required 
flue  area  in  square  feet. 

Example.  A  schoolroom  on  the  second  floor  is  to  have  an  air-supply  of 
2,000  cubic  feet  per  minute.  What  will  be  the  required  flue  area? 

ANS.     2000  -=-  340  =  5.8  +  sq.  feet. 

The  velocities  would  be  higher  in  the  coldest  weather,  and  dampers 
should  be  placed  in  the  flues  for  throttling  the  air-supply  when  nec- 
essary. 

Cold=Air  Ducts.  The  cold-air  ducts  supplying  heaters  should 
be  planned  in  a  manner  similar  to  that  described  for  furnace  heating. 
The  air-inlet  should  be  on  the  north  or  west  side  of  the  building;  but 
this  of  course  is  not  always  possible.  The  method  of  having  a  large 
trunk  line  or  duct  with  inlets  on  two  or  more  sides  of  the  building, 
should  be  carried  out  when  possible.  A  cold-air  room  with  large 
inlet  windows,  and  ducts  connecting  with  the  heaters,  makes  a  good 
arrangement  for  schoolhouse  work.  The  inlet  windows  in  this  case 
should  be  provided  with  check-valves  to  prevent  any  outward  flow  of 
air.  A  detail  of  this  arrangement  is  shown  in  Fig.  66. 

This  consists  of  a  boxing  around  the  window,  extending  from 
the  floor  to  the  ceiling.  The  front  is  sloped  as  shown,  and  is  closed 
from  the  ceiling  to  a  point  below  the  bottom  of  the  window.  The 
remainder  is  open,  and  covered  with  a  wire  netting  of  about  J-inch 
mesh;  to  this  are  fastened  flaps  or  checks  of  gossamer  cloth  about 
6  inches  in  width.  These  are  hemmed  on  both  edges  and  a  stout 
wire  is  run  through  the  upper  hem  which  is  fastened  to  the  netting 
by  means  of  small  copper  or  soft  iron  wire.  The  checks  allow  the  air 
to  flow  inward  but  close  when  there  is  any  tendency  for  the  current 
to  reverse. 

The  area  of  the  cold-air  duct  for  any  heater  should  be  about 
three-fourths  the  total  area  of  the  warm-air  ducts  leading  from^it. 


HEATING  AND  VENTILATION 


83 


If  the  duct  is  bf  any  considerable  length  or  contains  sharp  bends,  it 
should  be  made  the  full  size  of  all  the  warm-air  ducts.  Adjusting 
dampers  should  be  placed  in  the  supply  duct  to  each  separate  stack. 
If  a  trunk  with  two-inlets  is  used,  each  inlet  should  be  of  sufficient 
size  to  furnish  the  full  amount  of  air  required,  and  should  be  pro- 
vided with  cloth  checks  for  preventing  an  outward  flow  of  air,  as 
already  described.  The  inlet  windows  should  be  provided  with 
some  form  of  damper  or  slide,  outside  of  which  should  be  placed  a 
wire  grating,  backed  by  a  netting  of  about  f-inch  mesh. 

Vent  Flues.  In  dwelling-houses,  vent  flues  are  often  omitted, 
and  the  frequent  opening  of  doors  and  leakage  are  depended  upon  to 
carry  away  the  im- 
pure air.  A  well- 
designed  system  of 
warming  should 
provide  some  means 
for  discharge  ven- 
tilation, especially 
for  bathrooms  and 
toilet-rooms,  and 
also  for  living  rooms 
where  lights  are 
burned  in  the  even- 
ing. Fireplaces  are 
usually  provided  in 
the  more  important 
rooms  of  a  well- 
built  house,  and 
these  are  made  to 

serve  as  vent  flues.  In  rooms  having  no  fireplaces,  special  flues 
of  tin  or  galvanized  iron  may  be  carried  up  in  the  partitions  in 
the  same  manner  as  the  warm-air  flues.  These  should  be  gathered 
together  in  the  attic,  and  connected  with  a  brick  flue  running  up 
beside  the  boiler  or  range  chimney. 

Very  fair  results  may  be  obtained  by  simply  letting  the  flues  open 
into  an  unfinished  attic,  and  depending  upon  leakage  through  the 
roof  to  carry  away  the  foul  air. 


Fig.  66.    Air-Inlet  Provided  with  Check-Valves  to  Prevent 
Outward  Flow  of  Air. 


84 


HEATING  AND  VENTILATION 


The  sizes  of  flues  may  be  made  the  reverse  of  the  warm-air  flues 
—that  is,  1J  square  inches  area  per  square  foot  of  indirect  radiation 
for  rooms  on  the  first  floor,  and  2  square  inches  for  those  on  the 
second.  This  is  because  the  velocity  of  flow  will  depend  upon  the 
height  of  flue,  and  will  therefore  be  greater  from  the  first  floor.  The 
flow  of  air  through  the  vents  will  be  slow  at  best,  unless  some  means 
is  provided  for  warming  the  air  in  the  flue  to  a  temperature  above 
that  of  the  room  with  which  it  connects. 

The  method  of  carrying  up  the  outboard  discharge  beside  a  warm 
chimney  is  usually  sufficient  in  dwelling-houses;  but  when  it  is 

desired  to  move  larger 
quantities  of  air,  a  loop 
of  steam  pipe  should  be 
run  inside  the  flue.  This 
should  be  connected  for 
drainage  and  air-venting 
as  shown  in  Fig.  67. 
When  vents  are  carried 
through  the  roof  inde- 
pendently, some  form  of 
protecting  hood  should 
be  provided  for  keeping 
out  the  snow  and  rain. 
A  simple  form  is  shown 
in  Fig.  68.  Flues  carried 
outboard  in  this  way 
should  always  be  ex- 

.  tended   well   above   the   ridges  of  adjacent  roofs  to  prevent   down 
drafts  in  windy  weather. 

For  schoolhouse  work  we  may  assume  average  velocities  through 
the  vent  flues,  as  follows: 


Air 
Valve 


Ste<am 


Return 


Fig.  67.    Loop  of  Steam  Pipe  to  be  Run  Inside  Flue. 
Connected  for  Drainage  and  Air- Venting. 


1st  floor,  340  feet  per  minute. 
2nd     "  ,  280    "      "        " 
3rd     "  ,  220    "      " 


Where  flue  sizes  are  based  on  these  velocities,  it  is  well  to  guard 
against  down  drafts  by  placing  an  aspirating  coil  in  the  flue.  A 
single  row  of  pipes  across  the  flue  as  shown  in  Fig.  69,  is  usually 
sufficient  for  this  purpose  when  the  flues  are  large  and  straight; 


HEATING  AND  VENTILATION 


85 


otherwise,  two  rows  should  be  provided.  The  slant  height  of  the 
heater  should  be  about  twice  the  depth  of  the  flue,  so  that  the  area 
between  the  pipes  shall  equal  the 
free  area  of  the  flue. 

Large  vent  flues'of  this  kind 
should  always  be  provided  with 
dampers  for  closing  at  night,  and 
for  regulation  during  strong  winds. 

Sometimes  it  is  desired  to  move 
a  given  quantity  of  air  through  a 
flue  which  is  already  in  place. 
Table  XXIV  shows  what  velocities 
may  be  obtained  through  flues  of 
different  heights,  for  varying  dif- 
ferences in  temperature  between  the 
outside  air  and  that  in  the  flue. 

Example. — It  is  desired  to  discharge  1,300  cubic  feet  of  air  per  minute 
through  a  flue  having  an  area  of  4  square  feet  and  a  height  of  30  feet.  If  the 
efficiency  of  an  aspirating  coil  is  400  B.  T.  U.,  how  many  square  feet  of  surface 
will  be  required  to  move  this  amount  of  air  when  the  temperature  of  the  room 
is  70°  and  the  outside  temperature  is  60°? 


Fig.  68.    Section  Showing  Simple  Form 
of  Protecting  Hood  for  Vent  Car- 
ried through  Roof. 


I 


Fig.  69.    Aspirating  Coil  Placed  in  Flue  to  Prevent  Down  Drafts. 

1,300  +  4  =  325  feet  per  minute  =  Velocity  through  the  flue. 
Looking  in  Table  XXIV,  and  following  along  the  line  opposite  a 
30-foot  flue,  we  find  that  to  obtain  this  velocity  there  must  be  a  differ- 
ence of  30  degrees  between  the  air  in  the  flue  and  the  external  air. 


86 


HEATING  AND  VENTILATION 


If  the  outside  temperature  is  60  degrees,  then  the  air  in  the  flue  must 
be  raised  to  60  +  30  =  90  degrees.  The  air  of  the  room  being  at 
70  degrees,  a  rise  of  20  degrees  is  necessary.  So  the  problem  resolves 
itself  into  the  following:  What  amount  of  heating  surface  having  an 

TABLE  XXIV 

Air-Flow  through  Flues  of  Various  Heights  under  Varying 
Conditions  of  Temperature 

(Volumes  given  in  cubic  feet  per  square  foot  of  sectional  area  of  flue) 


HEIGHT  OF 
FLUE 
IN  FEET 

EXCESS  OF  TEMPERATURE  OF  AIR  IN  FLUE  ABO^E  THAT  OF  EXTERNAL  AIR 

5° 

10° 

15° 

20° 

30° 

50° 

5 

55 

76 

94 

109 

134 

167 

10 

77 

108 

133 

153 

188 

242 

15 

94 

133 

162 

188 

230 

297 

20 

108 

153 

188 

217 

265 

342 

25 

121 

171 

210 

242 

297 

383 

30 

133 

188 

230 

265 

325 

419 

35 

143 

203 

248 

286 

351 

453 

40 

153 

217 

265 

306 

375 

484 

45 

162 

230 

282 

325 

398 

514 

50 

171 

242 

297 

342 

419 

541 

60 

188 

264 

.  325 

373 

461 

594 

efficiency  of  400  B.  T.  U.  is  necessary  to  raise  1,300  cubic  feet  of  air 
per  minute  through  20  degrees? 

1,300  cubic  feet  per  minute  ==  1,300  X  60  ==  78,000  per  hour; 

and  making  use  of  our  formula  for  "heat  for  ventilation/'  we  have 

78,000  X  20 


55 


-28,363  B.T.U.; 


and  this  divided  by  400  =  71  square  feet  of  heating  surface  required. 

EXAMPLES    FOR    PRACTICE 

• 

1.  A  schoolroom  on  the  third  floor  has   50   pupils,  who   are 
to  be  furnished  with  30  cubic  feet  of  air  per  minute  each.     What  will 
be  the  required  areas  in  square  feet  of  the  supply  and  vent  flues? 

ANS.  Supply,  3.7  +.    Vent,  6.8  +. 

2.  What  size  of  heater  will  be  required  in  a  vent  flue  40  feet 
high  and  with  an  area  of  5  square  feet,  to  enable  it  to  discharge  1,530 
cubic  feet  per  minute,  when  the  outside  temperature  is  60°?     (Assume 
an  efficiency  of  400  B.  T.  U.  for  the  heater.)     ANS.  41 .7  square  feet. 


CONE    EXHAUST    FAN,    INLET    SIDE. 

American  Blower  Co. 


HEATING  AND  VENTILATION 


87 


Registers.    Registers  are  made  of  cast  iron  and  bronze,  in  a 
great  variety  of  sizes  and  patterns.     The  almost  universal  finish  for 
cast-iron  registers  is  black  ''Japan;"  but  they  are  also  finished  in 
colors  and  electroplated  with 
copper   and   nickel>  Fig.    70 
shows    a    section    through    a 
floor  register,  in  which  A  rep- 
resents the  valves,  which  may 
be  turned  in  a  vertical  or  hori- 
zontal position,  thus  opening 


Fig.  70.    Section  through  a  Floor  Register. 


or  closing  the  register;  B  is  the 
iron  border;  C,  the  register  box 
of  tin  or  galvanized  iron;  and  D,  the  warm-air  pipe.  Floor  registers 
are  usually  set  in  cast-iron  borders,  one  of  which  is  shown  in  Fig.  71 ; 
while  wall  registers  may  be  screwed  directly  to  wooden  borders  or 
frames  to  correspond  with  the  finish  of  the  room.  Wall  registers 
should  be  provided  with  pull-cords  for  opening  and  closing  from  the 
floor?  these  are  shown  in  Fig.  72.  The  plain  lattice  pattern  shown  in 
Fig.  73  is  the  best  for  schoolhouse-  work,  as  it  has  a  comparatively 

free  opening  for 
air-flow  and  is 
pleasing  and  sim- 
p  1  e  in  design. 
More  elaborate 
patterns  are  used 
for  fine  dwelling- 


house  work. 
Registers  with 
shut-off  valves 
are  used  for  air- 
inlets,  while  the 
plain  register 
faces  without  the 
valves  are  placed 
in  the  vent  open- 
ings. The  vent  flues  are  usually  gathered  together  in  the  attic,  and 
a  single  damper  may  be  used  to  shut  off  the  whole  number  at  once, 
Flat  or  round  wire  gratings  of  open  pattern  are  often  used  in  place  of 


Fig.  71.    Cast-Iron  Border  for  a  Floor  Register. 


88 


HEATING  AND  VENTILATION 


register  faces.  The  grill  or  solid  part  of  a  register  face  usually  takes 
up  about  J  of  the  area;  hence  in  computing  the  size,  we  must  allow 
for  this  by  multiplying  the  required  "net  area"  by  1.5,  to  obtain  the 
"total"  or  "over-all"  area. 

Example.  Suppose  we  have  a  flue  10  inches  in  width  and  wish  to  use  a 
register  having  a  free  area  of  200  square  inches.  What  will  be  the  required 
height  of  the  register? 

200  X  1 . 5  =  300  square  inches,  which  is  the  total  area  required ; 
then  300  -*-  10  =  30,  which  is  the  required  height,  and  we  should  use 
a  10  by  30-inch  register.  When  a  register  is  spoken  of  as  a  10  by 


Fig.  72.    Wall  Register  with  Pull 

Cords  for  Opening  and 

Closing. 


Fig.  73.    Plain  Lattice  Pattern  Register, 
for  Schoolhouse  Work. 


Best 


30-inch  or  a  10  by  20-inch,  etc.,  the  dimensions  of  the  latticed  opening 
are  meant,  and  not  the  outside  dimensions  of  the  whole  register.  The 
free  opening  should  have  the  same  area  as  the  flue  with  which  it  con- 
nects. In  designing  new  work,  one  should  provide  himself  with  a 
trade  catalogue,  and  use  only  standard  sizes,  as  special  patterns  and 
sizes  are  costly.  Fig.  74  sh^ws  the  method  of  placing  gossamer 
check-valves  back  of  the  v<  "*  ?gister  faces  to  prevent  down  drafts, 
the  same  as  described  :  r  fr  r  inlets. 


HEATING  AND  VENTILATION 


89 


Inlet  registers  in  dwelling-house  and  similar  work  are  placed 
either  in  the  floor  or  in  the  baseboard;  sometimes  they  are  located 
under  the  windows,  just  above  the  baseboard.  The  object  in  view 
is  to  place  them  where  the  currents  of  air  entering  the  room  will  not 
be  objectionable  to  persons  sitting  near  windows.  A  long,  narrow 
floor-register  placed  close  to  the  wall  in  front  of  a  window,  sends 
up  a  shallow  current  of  warm  air,  which  is  not  especially  noticeable 


N 


GOSSAMER 
CHECKS 


WIRE 
NETTING 


Fig.  74.    Method  of  Placing  Gossamer  Check- Valves  back  of  Vent  Register  Face 
to  Prevent  Down  Drafts. 

to  one  sitting  near  it.  Inlet  registers  are  preferably  placed  near 
outside  walls,  especially  in  large  rooms.  Vent  registers  should  be 
placed  in  inside  walls,  near  the  floor. 

Pipe  Connections.  The  two-pipe  system  with  dry  or  sealed 
returns  is  used  in  indirect  heating.  The  conditions  to  be  met  are 
practically  the  same  as  in  direct  heating,  the  only  difference  being 
that  the  radiators  are  at  the  basement  ceiling  instead  of  on  the  floors 
above.  The  exact  method  of  making  the  pipe  connections  will 
depend  somewhat  upon  existing  conditions;  but  the  general  method 
shown  in  Fig.  75  may  be  used  as  a  guide,  with  modifications  to  suit 


90 


HEATING  AND  VENTILATION 


any  special  case.    The  ends  of  all  supply  mains  should  be  dripped, 
and  the  horizontal  returns  should  be  sealed  if  possible. 

Pipe  Sizes.  The  tables  already  given  for  the  proportioning  of 
pipe  sizes  can  be  used  for  indirect  systems.  The  following  table  has 
been  computed  for  an  efficiency  of  640  B.  T.  U.  per  square  foot  of 
surface  per  hour,  which  corresponds  to  a  condensation  of  f  of  a  pound 
of  steam.  This  is  twice  that  allowed  for  direct  radiation  in  Table 


DR/P 


WATER         L/NE 


RETURN 


Fig.  75.    General  Method  of  Making  Pipe  and  Radiator  Connections,  in  Basement, 
in  Indirect  Heating. 

XVII;  so  that  we  can  consider  1  square  foot  of  indirect  surface  as 
equal  to  2  of  direct  in  computing  pipe  sizes. 

As  the  indirect  heaters  are  placed  in  the  basement,  care  must  be 
taken  that  the  bottom  of  the  radiator  does  not  come  too  near  the 
water-line  of  the  boiler,  or  the  condensation  will  not  flow  back  prop- 
erly; this  distance,  under  ordinary  conditions,  should  not  be  less  than 
2  feet.  If  much  less  than  this,  the  pipes  should  be  made  extra  large, 
so  that  there  may  be  little  or  no  drop  in  pressure  between  the  boiler 


HEATING  AND  VENTILATION 


91 


TABLE    XXV 
Indirect  Radiating  Surface  Supplied  by  Pipes  of  Various  Sizes 


SQUARE  FEET  OF  INDIRECT  RADIATION  WHICH  WILL  BE  SUPPLIED  WITH 


i  Pound  Crop  in  200  Feet 

4  Pound  Drop  in  100  Feet 

i  Pound  Drop  in  100  Feet 

1  iii. 

28 

40 

57 

H 

51 

72 

105 

lj 

67 

95 

170 

2 

185 

262 

375 

2* 

335 

475 

675      - 

3 

540 

775 

1,  105 

3* 

812 

1,160 

1,645 

1,  140 

1,625 

2,310 

5 

2,030 

2,900 

4,  110 

6 

3,260 

4,660 

6,  600 

7 

4,830 

6,900 

9,810 

8 

6,800 

9,720 

13,860 

and  the  heater.     A  drop  in  pressure  of  1   pound  would  raise  the 
water-line  at  the  heater  2.4  feet. 


Fig.  76.    General  Form  of  Direct-Indirect 
Radiator. 


Fig.  77.    Section  through  Radiator  Shown 
in  Fig.  76. 


Direct=Indirect  Radiators.     A  direct-indirect  radiator  is  similar 
in  form  to  a  direct  radiator,  and  is  placed  in  a  room  in  the  same 


92  HEATING  AND  VENTILATION 

manner.  Fig.  76  shows  the  general  form  of  this  type  of  radiator; 
and  Fig.  77  shows  a  section  through  the  same.  The  shape  of  the 
sections  is  such,  that  when  in  place,  small  flues  are  formed  between 
them.  Air  is  admitted  through  an  opening  in  the  outside  wall;  and, 
in  passing  upward  through  these  flues,  becomes  heated  before  enter- 
ing the  room.  A  switch-damper  is  placed  in  the  duct  at  the  base  of 
the  radiator,  so  that  the  air  may  be  taken  from  the  room  itself  instead 
'  f  from  out  of  doors,  if  so  desired.  This  is  shown  rnore  particularly 
in  Fig.  76. 

Fig.  78  shows  the  wall  box  provided  with  louvre  slats  and  netting, 
through  which  the  air  is  drawn.  A  damper  door  is  placed  at  either 

end  of  the  radiator  base ; 
and,  if  desired,  when  the 
cold-air  supply  is  shut  off 
by  means  of  the  register 
in  the  air-duct,  the  radia- 
tor can  be  converted  into 
the  ordinary  type  by 
opening  both  damper 

Fig.  78.    Wall  Box  with  Louvre  Slats  and  Netting,  doors,  thus  taking  the  air 

Direct-Indirect  System.  P  ,  i  •  '  i 

trom  the    room    instead 

of  from  the  outside.  It  is  customary  to  increase  the  size  of  a  direct- 
indirect  radiator  30  per  cent  above  that  called  for  in  the  case  of 
direct  heating. 

CARE  AND  MANAGEMENT  OF  STEAM= 
HEATING  BOILERS 

Special  directions  are  usually  supplied  by  the  maker  for  each 
kind  of  boiler,  or  for  those  which  are  to  be  managed  in  any  peculiar 
way.  The  following  general  directions  apply  to  all  makes,  and  may 
be  used  regardless  of  the  type  of  boiler  employed : 

Before  starting  the  fire,  see  that  the  boiler  contains  sufficient 
water.  The  water-line  should  be  at  about  the  center  of  the  gauge- 
glass. 

The  smoke-pipe  and  chimney  flue  should  be  clean,  and  the  draft 
good. 

Build  the  fire  in  the  usual  way,  using  a  quality  of  coal  which  is 
best  adapted  to  the  heater.  In  operating  the  fire,  keep  the  firepot 


HEATING  AND  VENTILATION  93 

full  of  coal,  and  shake  down  and  remove  all  ashes  and  cinders  as  often 
as  the  state  of  the  fire  requires  it. 

Hot  ashes  or  cinders  must  not  be  allowed  to  remain  in  the  ashpit 
under  the  grate-bars,  but  must  be  removed  at  regular  intervals  to 
prevent  burning  oufrthe  grate. 

To  control  the  fire,  see  that  the  damper  regulator  is  properly 
attached  to  the  draft  doors  and  the  damper;  then  regulate  the  draft 
by  weighting  the  automatic  lever  as  may  be  required  to  obtain  the 
necessary  steam  pressure  for  warming.  Should  the  water  in  the 
boiler  escape  by  means  of  a  broken  gauge-glass,  or  from  any  other 
cause,  the  fire  should  be  dumped,  and  the  boiler  allowed  to  cool  before 
adding  cold  water. 

An  empty  boiler  should  never  be  filled  when  hot.  If  the  water 
gets  low  at  any  time,  but  still  shows  in  the  .gauge-glass,  more  water 
should  be  added  by  the  means  provided  for  this  purpose. 

The  safety-valve  should  be  lifted  occasionally  to  see  that  it  is 
in  working  order. 

If  the  boiler  is  used  in  connection  with  a  gravity  system,  it  should 
be  cleaned  each  year  by  filling  with*  pure  water  and  emptying  through 
the  blow-off.  If  it  should  become  foul  or  dirty,  it  can  be  thoroughly 
cleansed  by  adding  a  few  pounds  of  caustic  soda,  and  allowing  it  to 
stand  for  a  day,  and  then  emptying  and  thoroughly  rinsing. 

During  the  summer  months,  it  is  recommended  that  the  water 
be  drawn  off  from  the  system,  and  that  air-valves  and  safety-valves 
be  opened  to  permit  the  heater  to  dry  out  and  to  remain  so.  Good 
results,  however,  are  obtained  by  filling  the  heater  full  of  water, 
driving  off  the  air  by  boiling  slowly,  and  allowing  it  to  remain  in  this 
condition  until  needed  in  the  fall.  The  water  should  then  be  drawn 
off  and  fresh  water  added. 

The  heating  surface  of  the  boiler  should  be  kept  clean  and  free  from 
ashes  and  soot  by  means  of  a  brush  made  especially  for  this  purpose. 

Should  any  of  the  rooms  fail  to  heat,  examine  the  steam  valves 
in  the  radiators.  If  a  two-pipe  system,  both  valves  at  each  radiator 
must  be  opened  or  closed  at  the  same  time,  as  required.  See  that 
the  air-valves  are  in  working  condition. 

If  the  building  is  to  be  unoccupied  in  cold  weather,  draw  all  the 
water  out  of  the  system  by  opening  the  blow-off  pipe  at  the  boiler  and 
all  steam  valves  and  air-valves  at  the  radiators. 


94 


HEATING  AND  VENTILATION 


HOT= WATER    HEATERS 

Types.  Hot-water  heaters  differ  from  steam  boilers  principally 
in  the  omission  of  the  reservoir  or  space  for  steam  above  the  heating 
surface.  The  steam  boiler  might  answer  as  a  heater  for  hot  water; 

but  the  large  capacity 
left  for  the  steam  would 
tend  to  make  its  opera- 
tion slow  and  rather 
unsatisfactory,  although 
the  same  type  of  boiler 
is  sometimes  used  for 
both  steam  and  hot 
water.  The  passages  in 
a  hot-water  heater  need 
not  extend  so  directly 
from  bottom  to  top  as 
in  a  steam  boiler,  since 
the  problem  of  provid- 
ing for  the  free  liberation 
of  the  steam  bubbles 
does  not  have  to  be  con- 
sidered. In  general,  the 
heat  from  the  furnace 
should  strike  the  sur- 
faces in  such  a  manner 
as  to  increase  the  natural 
circulation;  this  may  be. 
accomplished  to  a  cer- 
tain extent  by  arranging 
the  heating  surface  so 
that  a  large  proportion 
of  the  direct  heat  will 
be  absorbed  near  the 
top  of  the  heater. 
Practically  the  boilers  for  low-pressure  steam  and  for  hot  water  differ 
from  each  other  very  little  as  to  the  character  of  the  heating  surface, 
so  that  the  methods  already  given  for  computing  the  size  of  grate 
surface,  horse-power,  etc.,  under  the  head  of  " Steam  Boilers,"  can  be 


Fig.  79.    Richardson  Sectional  Hot-Water  Heater. 


HEATING  AND  VENTILATION 


95 


used   with   satisfactory   results    in    the   case   of   hot- water  heaters. 

It  is  sometimes  stated  that,  owing  to  the  greater  difference  in  tem- 
perature between  the  furnace  gases  and  the  water  in  a  hot-water 
heater,  as  compared^  with  steam,  the  heating  surface  will  be  more 
efficient  and  a  smaller  heater  can  be  used.  While  this  is  true  to  a 
certain  extent,  different  authorities  agree  that  this  advantage  is  so 
small  that  no  account  should  be  taken  of  it,  and  the  general  propor- 
tions of  the  heater  should  be  calculated  in  the  same  manner  as  for 
steam.  Fig.  79  shows  a  form  of  hot-water  heater  made  up  of  slabs 
or  sections  similar  to  the  sectional  steam  boiler  shown  in  Part  I. 
The  size  can  be  increased  in  a  similar  manner,  by  adding  more 
sections.  In  this  case,  however,  the  boiler  is  increased  in  width  in- 
stead of  in  length.  This  has  an  advantage  in  the  larger  sizes,  as  a 
second  fire  door  can 
be  added,  and  all 
parts  of  the  grate 
can  be  reached  as 
well  in  the  large  sizes 
as  in  the  small. 

Fig.  80  shows  a 
different  form  of  sec- 
tional boiler,  in  which 
the  sections  are 
placed  one  above  an- 
other. These  boilers 
are  circular  in  form 
and  well  adapted  to 
dwelling-houses  and 
similar  work. 

Fig.  81  shows  another  type  of  cast-iron  heater  which  is  not  made 
in  sections.  The  space  between  the  outer  and  inner  shells  surround- 
ing the  furnace  is  filled  with  water,  and  also  the  cross-pipes  directly 
over  the  fire  and  the  drum  at  the  top.  The  supply  to  the  radiators 
is  taken  off  from  the  top  of  the  heater,  and  the  return  connects  at  the 
lowest  point. 

The  ordinary  horizontal  and  vertical  tubular  boilers,  with  various 
modifications,  are  used  to  a  considerable  extent  for  hot-water  heating, 


Fig.  80. 


Invincible"  Boiler,  with  Sections 

Superposed. 
Courtesy  of  American  Radiator  Co. 


96 


HEATING  AND  VENTILATION 


and  are  well  adapted  to  this  class  of  work,  especially  in  the  case  of 
large  buildings. 

Automatic  regulators  are  often  used  for  the  purpose  of  main- 
taining a  constant  temperature  of  the  water.  They  are  constructed 
in  different  ways — some  depend  upon  the  expansion  of  a  metal  pipe 
or  rod  at  different  temperatures,  and  others  upon  the  vaporization 

and  consequent  pres- 
sure of  certain  volatile 
liquids.  These  means 
are  usually  employed 
to  open  small  valves 
which  admit  water- 
pressure  under  rubber 
diaphragms;  and  these 
in  turn  are  connected 
by  means  of  chains 
with  the  draft  doors 
of  the  furnace,  and  so 
regulate  the  draft  as 
required  to  maintain 
an  even  temperature 
of  the  water  in  the 
heater.  Fig.  82  shows 
one  of  the  first  kind. 
A  is  a  metal  rod  placed 
in  the  flow  pipe  from 
the  heater,  and  is  so 
connected  with  the 
valve  B  that  when  the 
water  reaches  a  certain 

temperature  the  expansion  of  the  rod  opens  the  valve  and  admits 
water  from  the  street  pressure  through  the  pipes  C  and  D  into  the 
chamber  E.  .The  bottom  of  E  consists  of  a  rubber  diaphragm, 
which  is  forced  down  by  the  water-pressure  and  carries  with  it  the 
lever  which  operates  the  dampers  as  shown,  and  checks  the  fire. 
When  the  temperature  of  the  water  drops,  the  rod  contracts  and 
valve  B  closes,  shutting  off  the  pressure  from  the  chamber .  E.  A 
spring  is  provided  to  throw  the  lever  back  to  its  original  position, 


Fig.  81.    Cast-Iron  Heater  Not  Made  in  Sections.    Water 

Fills  Ci'oss-Pipes  and  Space  between  Outer  and 

Inner  Shells. 


HEATING  AND  VENTILATION 


97 


and  the  water  above  the  diaphragm  is  forced  out  through  the  pet- 
cock  G,  which  is  kept  slightly  open  all  the  time.  ' 

DIRECT  HOT=WATER  HEATING 

A  hot-water  system  is  similar  in  construction  and  operation  to 
one  designed  for  steam,  except  that  hot  water  flows  through  the 
pipes  and  radiators  instead. 

The  circulation  through  the  pipes  is  produced  solely  by  the  dif- 
ference in  weight  of  the 
water  in  the  supply  and 
return,  due  to  the  differ- 
e n c e  in  temperature. 
When  water  is  heated  it 
expands,  and  thus  a 
given  volume  becomes 
lighter  and  tends  to  rise, 
and  the  cooler  water  flows 
in  to  take  its  place ;  if  the 
application  of  heat  is  kept 
up,  the  circulation  thus 
produced  is  continuous. 
The  velocity  of  flow  de- 
pends upon  the  difference 
in  temperature  between 
the  supply  and  return, 
and  the  height  of  the 
radiator  above  the  boiler. 
The  horizontal  distance 
of  the  radiator  from  the 
boiler  is  also  an  important  factor  affecting  the  velocity  of  flow. 

This  action  is  best  shown  by  means  of  a  diagram,  as  in  Fig.  83. 
If  a  glass  tube  of  the  form  shown  in  the  figure  is  filled  with  water  and 
held  in  a  vertical  position,  no  movement  of  the  water  will  be  noticed, 
because  the  two  columns  A  and  B  are  of  the  same  weight,  and  there- 
fore in  equilibrium.  Now,  if  a  lamp  flame  be  held  near  the  tube  A, 
the  small  bubbles  of  steam  which  are  formed  will  show  the  water 
to  be  in  motion,  with  a  current  flowing  in  the  direction  indicated  by 
the  arrows.  The  reason  for  this  is,  that,  as  the  water  in  A  is  heated, 


Fig.  82.    Hot- Water  Heater  with  Automatic  Regu- 
lator Operated  through  Expansion  and  Con- 
traction of  Metal  Rod  in  Flow  Pipe. 


98 


HEATING  AND  VENTILATION 


Fig.  83.  Illustrating 
How  the  Heating 
of  Water  Causes 
Circulation. 


it  expands  and  becomes  lighter  for  a  given  volume,  and  is  forced 

upward  by  the  heavier  water  in  B  falling  to  the  bottom  of  the  tube. 

The  heated  water  flows  from  A  through  the  connecting  tube  at  the 
top,  into  B,  where  it  takes  the  place  of  the 
cooler  water  which  is  settling  to  the  bottom.  If, 
now,  the  lamp  be  replaced  by  a  furnace,  and  the 
columns  A  and  B  be  connected  at  the  top  by 
inserting  a  radiator,  the  illustration  will  assume 
the  practical  form  as  utilized  in  hot-water  heating 
(see  Fig.  84). 

The  heat  given  off  by  the  radiator  always 
insures  a  difference  in  temperature  between  the 
columns  of  water  in  the  supply  and  return  pipes, 
so  that  as  long  as  heat  is  supplied  by  the  furnace 
the  flow  of  water  will  continue.  The  greater  the 

difference  in  temperature  of  the  water  in  the  two  pipes,  the  greater 

the  difference  in  weight,  and  con- 
sequently the  faster  the  flow.     The 

greater  the  height  of  the  radiator 

above  the  heater,  the   more   rapid 

will  be  the  circulation,  because  the 

total  difference   in  weight  between 

the  water  in  the  supply  and  return 

risers  will  vary  directly  with  their 

height.    From  the  above  it  is  evident 

that  the  rapidity  of  flow  depends 

chiefly  upon  the  temperature  differ- 
ence between  the  supply  and  return, 

and  upon  the  height  of  the  radiator 

above  the  heater.     Another  factor 

which  must  be  considered  in  long 

runs  of  horizontal  pipe  is  the  fric- 

tional  resistance. 

Systems  of  Circulation.    There 

are    two    distinct   systems   of   cir- 
culation employed — one  depending 

on    the   difference    in    temperature 

of  the  water  in  the  supply  and  return  pipes,  called  gravity  circulation*. 


\ 


£X PANS/ ON    TANK 


RAD/ATOR 


Fig.  84.    Illustrating  Simple  Circula- 
tion in  a  Heating  System. 


HEATING  AND  VENTILATION 


and  another  where  a  pump  is  used  to  force  the  water  through  the 
mains,  called  forced  circulation.  The  former  is  used  for  dwellings 
and  other  buildings  of  ordinary  size,  and  the  latter  for  large  buildings, 
and  especially  where  there  are  long  horizontal  runs  of  pipe. 

For  gravity  circulation  some  form  of  sectional  cast-iron  boiler 
is  commonly  used,  although  wrought-iron  tubular  boilers  may  be 
employed  if  desired.  In  the  case  of  forced  circulation,  a  heater  de- 
signed to  warm  the  water  by  means  of  live  or  exhaust  steam  is  often 
used.  A  centrifugal  or  rotary  pump  is  best  adapted  to  this  pur- 
pose, and  may  be  driven  by  an  electric  motor  or  a  steam  engine, 
as  most  convenient. 

Types  of  Radiating  Surface.  Cast-iron  radiators  and  circulation 
coils  are  used  for  hot  water  as  ^^——m  }  -  — ^ 
well  as  for  steam.  Hot-water 
radiators  differ  from  steam 
radiators  principally  in  having 
a  horizontal  passage  at  the  top 
as  well  as  at  the  bottom. 
This  construction  is  necessary 
in  order  to  draw  off  the  air 
which  gathers  at  the  top  of 
each  loop  or  section.  Other- 
wise they  are  the  same  as 
steam  radiators,  and  are  well 
adapted  for  the  circulation  of 
steam,  and  in  some  respects 
are  superior  to  the  ordinary  pattern  of  steam  radiator. 

The  form  shown  in  Fig.  85  is  made  with  an  opening  at  the  top 
for  the  entrance  of  water,  and  at  the  bottom  for  its  discharge,  thus 
insuring  a  supply  of  hot  water  at  the  top  and  of  colder  water  at  the 
bottom. 

Some  hot-water  radiators  are  made  with  a  cross-partition  so 
arranged  that  all  water  entering  passes  at  once  to  the  top,  from  which 
it  may  take  any  passage  toward  the  outlet.  Fig.  86  is  the  more 
common  form  of  radiator,  and  is  made  with  continuous  passages  at 
top  and  bottom,  the  hot  water  being  supplied  at  one  side  and  drawn 
off  at  the  other.  The  action  of  gravity  is  depended  upon  for  making 
the  hot  and  lighter  water  pass  to  the  top,  and  the  colder  water  sink 


Fig.  85.    Showing  Construction  of  Radiator  for 
Hot  Water  or  Steam.    Note  Horizontal  Pas- 
sage along  Top. 


100 


HEATING  AND  VENTILATION 


to  the  bottom  and  flow  off  through  the  return.  Hot-water  radiators 
are  usually  tapped  and  plugged  so  that  the  pipe  connections  can  be 
made  either  at  the  top  or  at  the  bottom.  This  is  shown  in  Fig.  87. 

Wall  radiators  are  adapted  to  hot-water  as  well  as  steam  heating. 

Efficiency  of  Radiators.  The  efficiency  of  a  hot-water  radiator 
depends  entirely  upon  the  temperature  at  which  the  water  is  circu- 
lated. The  best  practical  results  are  obtained  with  the  water  leaving 
the  boiler  at  a  maximum  temperature  of  about  180  degrees  in  zero 
weather  and  returning  at  about  160  degrees;  this  gives  an  average 


Fig.  86.    Common  Form  of  Hot-Water  Radiator.  Circulation       Fig.  87.  End  Elevation  of 


Produced  Wholly  through  Action  of  Gravity,  Hot 
Water  Rising  to  Top. 


Radiator  Showing  Taps 
at  Top  and  Bottom  for 
Pipe  Connections. 


temperature  of  170  degrees  in  the  radiators.  Variations  may  be  made, 
however,  to  suit  the  existing  conditions  of  outside  temperature.  We 
have  seen  that  an  average  cast-iron  radiator  gives  off  about  1.7  B.T.U. 
per  hour  per  square  foot  of  surface  per  degree  difference  in  tempera- 
ture between  the  radiator  and  the  surrounding  air,  when  working 
under  ordinary  conditions;  and  this  holds  true  whether  it  is  filled 
with  steam  or  water. 

If  we  assume  an  average  temperature  of  170  degrees  for  the 
water,  then  the  difference  in  temperature  between  the  radiator  and 
the  air  will  be  170  —  70  =  100  degrees;  and  this  multiplied  by  1 .7  = 


HEATING  AND  VENTILATION 


101 


170,  which  may  be  taken  as  the  efficiency  of  a  hot-water  radiator 
under  the  above  average  conditions. 

This  calls  for  a  water  radiator  about  1 . 5  times  as  large  as  a  steam 
radiator  to  heat  a  given  room  under  the  same  conditions.  This  is 
common  practice  although  some  engineers  multiply  by  the  factor  1 . 6, 
which  allows  for  a  lower  temperature  of  the  water.  Water  leaving 
the  boiler  at  170  degrees  should  return  at  about  150;  the  drop  in 
temperature  should  not  ordinarily  exceed  20  degrees. 

Systems  of  Piping.  A  system  of  hot-water  heating  should  pro- 
duce a  perfect  circulation  of  water  from  the  heater  to  the  radiating 


Fig.  88.    System  of  Piping  Usually  Employed  for  Hot-Water  Heating. 

surface,  and  thence  back  to  the  heater  through  the  returns.  The 
system  of  piping  usually  employed  for  hot-water  heating  is  shown  in 
Fig.  88.  In  this  arrangement  the  main  and  branches  have  an  inclina- 
tion upward  from  the  heater;  the  returns  are  parallel  to  the  mains, 
and  have  an  inclination  downward  toward  the  heater,  connecting 
with  it  at  the  lowest  point.  The  flow  pipes  or  risers  are  taken  from 
the  tops  of  the  mains,  and  may  supply  one  or  more  radiators  as 
required.  The  return  risers  or  drops  are  connected  with  the  return 
mains  in  a  similar  manner.  In  this  system  great  care  must  be  taken 
to  produce  a  nearly  equal  resistance  to  flow  in  all  of  the  branches,  so 
that  each  radiator  may  receive  its  full  supply  of  water.  It  will  always 


102 


HEATING  AND  VENTILATION 


be  found  that  the  principal  current  of  heated  water  will  take  the  path 
of  least  resistance,  and  that  a  small  obstruction  or  irregularity  in  the 
piping  is  sufficient  to  interfere  greatly  with  the  amount  of  heat  received 
in  the  different  parts  of  the  same  system. 

Some  engineers  prefer  to  carry  a  single  supply  main  around  the 
building,  of  sufficient  size  to  supply  all  the  radiators,  bringing  back 
a  single  return  of  the  same  size.  Practice  has  shown  that  in  general 
it  is  not  well  to  use  pipes  over  8  or  10  inches  in  diameter;  if  larger 
pipes  are  required,  it  is  better  to  run  two  or  more  branches. 

The  boiler,  if  possible,  should  be  centrally  located,  and  branches 

carried  to  differ- 
ent  parts  of  the 
building.  This 
insures  a  more 
even  circulation 
than  if  all  the 
radiators  are 
supplied  from  a 
single  long  main, 
in  which  case 
the  circulation 
is  liable  to  be 
sluggish  at  the 
farther  end. 

The  arrange- 
ment shown  in 
Fig.  89  is  similar 


Fig.  89.    System  of  Hot- Water   Piping  Especially   Adapted   to 
Apartment  Buildings  where  Each  Flat  Has  a  Separate  Heater. 


to  the  circuit  system  for  steam,  except  that  the  radiators  have  two 
connections  instead  of  one.  This  method  is  especially  adapted  to 
apartment  houses,  where  each  flat  has  its  separate  heater,  as  it 
eliminates  a  separate  return  main,  and  thus  reduces,  by  practically 
one-half,  the  amount  of  piping  in  the  basement.  The  supply  risers 
are  taken  from  the  top  of  the  main;  while  the  returns  should  con- 
nect into  the  side  a  short  distance  beyond,  and  in  a  direction  away 
from  the  boiler.  When  this  system  is  used,  it  is  necessary  to  enlarge 
the  radiators  slightly  as  the  distance  from  the  boiler  increases. 

In  flats  of  eight  or  ten  rooms,  the  size  of  the  last  radiator  may  be 
increased  from  10  to  15  per  cent,  and  the  intermediate  ones  proper- 


DIRECT-INDIRECT    SYSTEM    OF    WARMING,    SHOWING   ADJUSTABLE    DAMPER. 

American  Radiator  Company. 


HEATING  AND  VENTILATION 


103 


tionally,  at  the  same  time  keeping  the  main  of  a  large  and  uniform 
size  for  the  entire  circuit. 

Overhead  Distribution.  This  system  of  piping  is  shown  in  Fig. 
90.  A  single  riser  is  carried  directly  to  the  expansion  tank,  from 
which  branches  are 'taken  to  supply  the  various  drops  to  which  the 
radiators  are  connected.  An  important  advantage  in  connection 
with  this  system  is  that  the  air  rises  at  once  to  thejexpansion  tank, 
and  escapes  through  the  vent,  so  that  air-valves  are  not  required  on 
the  radiators. 


xpa.tas-ioT-1  Tank 


Fig.  90.    "Overhead"  Distribution  System  of  Hot- Water  Piping. 

At  the  same  time,  it  has  the  disadvantage  that  the  water  in  the 
tank  is  under  less  pressure  than  in  the  heater;  hence  it  will  boil  at 
a  lower  temperature.  No  trouble  will  be  experienced  from  this,  how- 
ever, unless  the  temperature  of  the  water  is  raised  above  212  degrees. 

Expansion  Tank.  Every  system  for  hot- water  heating  should  be 
connected  with  an  expansion  tank  placed  at  a  point  somewhat  above 
the  highest  radiator.  The  tank  must  in  every  case  be  connected  to  a 
line  of  piping  which  cannot  by  any  possible  means  be  shut  off  from 
the  boiler0  When  water  is  heated,  it  expands  a  certain  amount, 


104 


HEATING  AND  VENTILATION 


OVERFLOW 


depending  upon  the  temperature  to  which  it  is  raised;  and  a  tank  or 

reservoir  should  always  be  provided  to  care  for  this  increase  in  volume. 

Expansion  tanks  are  usually  made  of  heavy  galvanized  iron  of 

one  of  the  forms  shown  in  Figs.  91  and  92,  the  latter  form  being  used 

where  the  headroom  is  limited.  The 
connection  from  the  heating  system 
enters  the  bottom  of  the  tank,  and 
an  open  vent  pipe  is  taken  from  the 
top.  An  overflow  connected  with 
a  sink  or  drain-pipe  should  be 
provided.  Connections  should  be 
made  with  the  water  supply  both 
at  the  boiler  and  at  the  expansion 
tank,  the  former  to  be  used  when 
first  filling  the  system,  as  by  this 
means  all  air  is  driven  from  the  bot- 
tom upward  and  is  discharged 
through  the  vent  at  the  expansion 

Fig.  91.    A  Common  Form  of  Galvanized-    fQT1T,-       Waf^r    fliat    i<j    arJrlprl     aftpr- 
Iron  Expansion  Tank.  tanK-       VV  at( 

ward  may  be  supplied  directly  to  the 

expansion  tank,  where  the  water-line  can  be  noted  in  the  gauge-glass. 
A  ball-cock  is  sometimes  arranged  to  keep  the  water-line  in  the  tank 
at  a  constant  level. 
An  altitude 
gauge   is    often 
placed  in  the  base- 
ment with  the  col- 
ored hand  or  point- 
er  set   to   indicate 
the  normal  water- 
line  in  the  expan- 
sion tank.      When 
the   movable  hand 


? 

?   .- 

CONfVE" 
FR 
SYS  7 

VCNT   P/PC 


OVERFLOW 


COHHCC  r/O/V 
FROM 


Fig.  92.    Form  of  Expansion  Tank  Used  where  Headroom 
is  Limited. 


falls  below- the 

fixed    one,    more 

water  may  be  added,  as  required,  through  the  supply  pipe  at  the  boiler. 

When  the  tank  is  placed  in  an  attic  or  roof  space  where  there  is  danger 

of  freezing,  the  expansion  pipe  may  be  connected  into  the  side  of  the 


HEATING  AND  VENTILATION  105 

tank,  6  or  8  inches  from  the  bottom,  and  a  circulation  pipe  taken 
from  the  lower  part  and  connected  with  the  return  from  an  upper- 
floor  radiator.  This  produces  a  slow  circulation  through  the  tank, 
and  keeps  the  water  warm. 

The  size  of  ther  expansion  tank  depends  upon  the  volume  of 
water  contained  in  the  system,  and  on  the  temperature  to  which  it  is 
heated.  The  following  rule  for  computing  the  capacity  of  the  tank 
may  be  used  with  satisfactory  results: 

Square  feet  of  radiation,  divided  by  40,  equals  required  capacity  of 
tank  in  gallons. 

Air=Venting.  One  very  important  point  to  be  kept  in  mind  in 
the  design  of  a  hot-water  system,  is  the  removal  of  air  from  the  pipes 
and  radiators.  When  the  water  in  the  boiler  is  heated,  the  air  it 
contains  forms  into  small  bubbles  which  rise  to  the  highest  points  of  the 
system. 

In  the  arrangement  shown  in  Fig.  88,  the  main  and  branches 
grade  upward  from  the  boiler,  so  that  the  air  finds  its  way  into  the 
radiators,  from  which  it  may  be  drawn  off  by  means  of  the  air-valves. 

A  better  plan  is  that  shown  in 'Fig.  89.  In  this  case  the  expan- 
sion pipe  is  taken  directly  off  the  top  of  the  main  over  the  boiler,  so 
that  the  larger  part  of  the  air  rises  directly  to  the  expansion  tank  and 
escapes  through  the  vent  pipe.  The  same  action  takes  place  in  the 
overhead  system  shown  in  Fig.  90,  where  the  top  of  the  main  riser 
is  connected  with  the  tank.  Every  high  point  in  the  system  and 
every  radiator,  except  in  the  downward  system  with  top  supply  con- 
nection, should  be  provided  with  an  air-valve. 

Pipe  Connections.  There  are  various  methods  of  connecting 
the  radiators  with  the  mains  and  risers.  Fig.  93  shows  a  radiator 
connected  with  the  horizontal  flow  and  return  mains,  which  are 
located  below  the  floor.  The  manner  of  connecting  with  a  vertical 
riser  and  return  drop  is  shown  in  Fig.  94.  As  the  water  tends  to 
flow  to  the  highest  point,  the  radiators  on  the  lower  floors  should  be 
favored  by  making  the  connection  at  the  top  of  the  riser  and  taking 
the  pipe  for  the  upper  floors  from  the  side  as  shown.  Fig.  95  illus- 
trates the  manner  of  connecting  with  a  radiator  on  an  upper  floor  where 
the  supply  is  connected  at  the  top  of  the  radiator. 

The  connections  shown  in  Figs.  96  and  97  are  used  with  the 
overhead  system  shown  in  Fig.  90. 


106. 


HEATING  AND  VENTILATION 


Where  the  connection  is  of  the  form  shown  at  the  left  in  Fig.  90, 
the  cooler  water  from  the  radiators  is  discharged  into  the  supply  pipe 
again,  so  that  the  water  furnished  to  the  radiators  on  the  lower  floors 
is  at  a  lower  temperature,  and  the  amount  of  heating  surface  must  be 
correspondingly  increased  to  make  up  for  this  loss,  as  already  de- 
scribed for  the  circuit  system. 


Fig.  93.    Radiator   Connected   with  Hori- 
zontal Flow  and  Return  Mains 
Located  below  Floor. 


Fig.  94.    Radiator  Connected  to  Vertical 
Riser  and  Return  Drop. 


For  example,  if  in  the  case  of  Fig.  90  we  assume  the  water  to 
leave  at  180  degrees  and  return  at  160,  we  shall  have  a  drop  in  tem- 
perature of  10  degrees  on  each  floor;  that  is,  the  water  will  enter  the 
radiator  on  the  second  floor  at  180  degrees  and  leave  it  at  170,  and 
will  enter  the  radiator  on  the  first  floor  at  170  and  leave  it  at  160. 


Fig.  95. 


Upper-Floor  Radiator  with  Sup- 
ply Connected  at  Top. 


Fig  96.    Radiator  Connections,  Overhead 
Distribution  System. 


The  average  temperatures  will  be  175  and  165,  respectively.  The 
efficiency  in  the  first  case  will  be  175  —  70  =  105;  and  105  X  1 .5  = 
157.  In  the  second  case,  165  —  70  =  95;  and  95  X  1.5  =  142; 
so  that  the  radiator  on  the  first  floor  will  have  to  be  larger  than  that 
on  the  second  floor  in  the  ratio  of  157  to  142,  in  order  to  do  the  same 
work. 


HEATING  AND  VENTILATION 


107 


This  is  approximately  an  increase  of  10  per  cent  for  each  story 
downward  to  offset  the  cooling  effect;  but  in  practice  the  supply 
drops  are  made  of  such  size  that  only  a  part  of  the  water  is  by-passed 
through  the  radiators.  For  this  reason  an  increase  of  5  per  cent 
for  each  story  downwaVd  is  probably  sufficient  in  ordinary  cases. 

Where  the  radiators  discharge 
into  a  separate  return  as  in  the  case 
of  Fig.  88,  or  those  at  the  right  in 
Fig.  90,  we  may  assume  the  tempera- 
ture of  the  water  to  be  the  same  on 
all  floors,  and  give  the  radiators  an 
equal  efficiency. 

In  a  dwelling-house  of  two  stories, 
no  difference  would  be  made  in  the 
sizes  of  radiators  on  the  two  floors; 
but  in  the  case  of  a  tall  office  build- 
ing, corrections  would  necessarily  be  made  as  above  described. 

Where  circulation  coils  are  used,  they  should  be  of  a  form  which 
will  tend  to  produce  a  flow  of  water  through  them.  Figs.  98,  99,  and 
100  show  different  ways  of  making  up  and  connecting  these  coils. 
In  Figs.  98  and  100,  supply  pipes  may  be  either  drops  or  risers;  and 


Fig.  97.    Another  Form  of  Radiator 
Connection,  Overhead  Distribu- 
tion System. 


Fig.  98.    Circulation  Coil,  One  Method  of  Construction.    Supply  Pipes 
may  be  Either  Drops  or  Risers. 


in  the  former  case  the  return  in  Fig.  100  may  be  carried  back,  if  desired, 
into  the  supply  drop,  as  shown  by  the  dotted  lines. 

Combination  Systems.  Sometimes  the  boiler  and  piping  are 
arranged  for  either  steam  or  hot  water,  since  the  demand  for  a  higher 
or  lower  temperature  of  the  radiators  might  change. 


108 


HEATING  AND  VENTILATION 


The  object  of  this  arrangement  is  to  secure  the  advantages  of  a 
hot-water  system  for  moderate  temperatures,  and  of  steam  heating 
for  extremely  cold  weather. 


Fig.  99.    Another  Method  of  Building  Up  a  Circulation  Coil. 

As  less  radiating  surface  is  required  for  steam  heating,  there  is 
an  advantage  due  to  the  reduction  in  first  cost.  This  is  of  consider- 
able importance,  as  a  heating  system  must  be  designed  of  such  dimen- 
sions as  to  be  capable  of  warming  a  building  in  the  coldest  weather; 


Fig.  100.    Circulation  Coil  with  Either  Drop  or  Riser  Supply.    In  former  case,  return 
may  be  carried  into  Supply  Drop  as  shown  by  Dotted  Lines. 

and  this  involves  the  expenditure  of  a  considerable  amount  for  radiat- 
ing surfaces,  which  are  needed  only  at  rare  intervals.  A  combination 
system  of  hot-water  and  steam  heating  requires,  first,  a  heater  or  boiler 


HEATING  AND  VENTILATION  100 


which  will  answer  for  either  purpose;  second,  a  system  of  piping 
which  will  permit  the  circulation  of  either  steam  or  hot  water;  and 
third,  the  use  of  radiators  which  are  adapted  to  both  kinds  of  heating. 
These  requirements  will  be  met  by  using  a  steam  boiler  provided  with 
all  the  fittings  requireoT  for  steam  heating,  but  so  arranged  that  the 
damper  regulator  may  be  closed  by  means  of  valves  when  the  system 
is  to  be  used  for  hot-water  heating.  The  addition  of  an  expansion 
tank  is  required,  which  must  be  so  arranged  that  it  can  be  shut  off 
when  the  system  is  used  for  steam  heating.  The  system  of  piping 
shown  in  Fig.  88  is  best  adapted  for  a  combination  system,  although 
an  overhead  distribution  as  shown  in  Fig.  90  may  be  used  by  shutting 
off  the  vent  and  overflow  pipes,  and  placing  air-valves  on  the  radiators. 

While  this  system  has  many  advantages  in  the  way  of  cost  over 
the  complete  hot-water  system,  the  labor  of  changing  from  steam 
to  hot  water  will  in  some  cases  be  trouble- 
some; and  should  the  connections  to  the 
expansion  tank  not  be  opened,  serious  re- 
sults would  follow. 

Valves  and  Fittings.  Gate-valves 
should  always  be  used  in  connection  with 
hot-water  piping,  although  angle-valves  may 
be  used  at  the  radiators.  There  are  several 
patterns  of  radiator  valves  made  especially 
for  hot-water  work;  their  chief  advantage 
lies  in  a  device  for  quick  closing,  usually  a  Fig.101.  Radiator  Valvefor 
quarter-turn  or  half-turn  being  sufficient  to 

open  or  close  the  valve.  Two  different  designs  are  shown  in  Figs. 
101  and  102. 

It  is  customary  to  place  a  valve  in  only  one  connection,  as  that  is 
sufficient  to  stop  the  flow  of  water  through  the  radiator;  a  fitting 
known  as  a  union  elbow  is  often  employed  in  place  of  the  second  valve. 
(See  Fig.  103.) 

Air=Valves.  The  ordinary  pet-cock  air-valve  is  the  most  reliable 
for  hot-water  radiators,  although  there  are  several  forms  of  auto- 
matic valves  which  are  claimed  to  give  satisfaction.  One  of  these 
is  shown  in  Fig.  104.  This  is  similar  in  construction  to  a  steam 
trap.  As  air  collects  in  the  chamber,  and  the  water-line  is  lowered, 
the  float  drops,  and  in  so  doing  opens  a  small  valve  at  the  top  of  the 


110 


HEATING  AND  VENTILATION 


chamber,  which  allows  the  air  to  escape.     As  the  water  flows  in  to  take 
its  place,  the  float  is  forced  upward  and  the  valve  is  closed. 

All  radiators  which  are  supplied  by  risers  from  below,  should  be 
provided  with  air-valves  placed  in  the  top 
of  the  last  section  at  the  return  end.  If 
they  are  supplied  by  drops  from  an  over- 


Fig.  102.    Another  Type  of  Hot- 
Water  Radiator  Valve. 


Fig.  103.    Union  Elbow. 


head  system,  the  air  will  be  discharged  at  the   expansion  tank,  and 

air-valves  will  not  be  necessary  at  the  radiators. 

Fittings.    All  fittings,  such  as  elbows,  tees,  etc.,  should  be  of 

the  long-turn  pattern.     If  the  common  form  is  used,  they  should  be 

a  size  larger  than  the  pipe,  bushed 
down  to  the  proper  size.  The  long- 
turn  fittings,  however,  are  preferable, 
and  give  a  much  better  appearance. 
Connections  between  the  radiators 
and  risers  may  be  made  with  the 
ordinary  short-pattern  fittings,  as 
those  of  the  other  form  are  not  well 
adapted  to  the  close  connections  nec- 
essary for  this  work. 

Pipe  Sizes.  The  size  of  pipe 
required  to  supply  any  given  radiator 
depends  upon  four  conditions  ;  first,  the 
size  of  the  radiator  ;  second,  its  elevation 

nUnvP  fV,P  KniW'  third  flip  Ipno-th  nf 
aDOVC  QT  ,  I/lira,  I 

pipe  required  to  connect  it  with  the 
boiler;  and  fourth,  the  difference  in  temperature  between  the  supply 
and  the  retura 


Fig.  104.     Automatic   Air-Valve  for 
Hot-  Water  Radiator.    Operated 


HEATING  AND  VENTILATION 


111 


As  it  would  be  a  long  and  rather  complicated  process  to  work  out 
the  required  size  of  each  pipe  for  a  heating  system,  Tables  XXVI  and 
XXVII  have  been  prepared,  covering  the  usual  conditions  to  be  met 
with  in  practice. 

TABLE   XXVI 

Direct  Radiating  Surface  Supplied  by  Mains  of  Different 
Sizes  and  Lengths  of  Run 


SQUARE  FEET  OF  RADIATING  SURFACE 


Ol/.r-    <->.r     •*•  irrj 

100  ft. 
Run 

200   ft. 
Run 

300   ft. 
Run 

400    ft. 
Run 

500  ft, 
Run 

600  ft. 
Run 

700   ft. 
Run 

800  ft. 
Run 

1,000 
ft.  Run 

1    in. 

30 

u* 

60 

50 

ir 

100 

75 

50 

2    ' 

200 

150 

125 

100 

75 

2*' 

350 

250 

200 

175 

150 

125 

3    ' 

550 

400 

300 

275 

250 

225 

200 

175 

150 

3*' 

850 

600 

450 

400 

350 

325 

300 

250 

225 

4    ' 

1,200 

850 

700 

600 

525 

475 

450 

400 

350 

5    ' 

1,400 

1,150 

1,000 

700 

850 

775 

725 

650 

6    ' 

1,600 

1,400 

1,300 

1,200 

1,150 

1,000 

7    ' 

1,706 

1,600 

1,500 

These  quantities  have  been  calculated  on  a  basis  of  10  feet  difference 
in  elevation  between  the  center  of  the  heater  and  the  radiators,  and  a  differ- 
ence in  temperature  of  17  degrees  between  the  supply  and  the  return. 

TABLE  XXVII 

Radiating  Surface  on  Different  Floors  Supplied  by 
Pipes  of  Different  Sizes 


SIZE  OF 


SQUARE  FEET  OF  RADIATING  SURFACE 


1st    Story 

2d  Story 

3d  Story 

4th  Story 

5th  Story 

6th  Story 

1     in. 

30 

55 

65 

75 

85 

95 

1M     - 

60 

90 

110 

125 

140 

160 

\y2 

100 

140 

165 

185 

210 

240 

2 

200 

275 

375 

425 

500 

21/2 

350 

475 

3 

550 

sy2 

850 

Table  XXVI  gives  the  number  of  square  feet  of  direct  radiation 
which  different  sizes  of  mains  and  branches  will  supply  for  varying 
lengths  of  run. 

Table  X*XVI  may  be  used  for  all  horizontal  mains.  For  vertical 
risers  or  drops,  Table  XXVII  may  be  used.  This  has  been  com- 


112  HEATING  AND  VENTILATION 

puted  for  the  same  difference  in  temperature  as  in  the  case  of  Table 
XXVI  (17  degrees),  and  gives  the  square  feet  of  surface  which  dif- 
ferent sizes  of  pipe  will  supply  on  the  different  floors  of  a  building, 
assuming  the  height  of  the  stories  to  be  10  feet.  Where  a  single 
riser  is  carried  to  the  top  of  a  building  to  supply  the  radiators  on  the 
floors  below,  by  drop  pipes,  we  must  first  get  what  is  called  the  average 
elevation  of  the  system  before  taking  its  size  from  the  table.  This  may 
be  illustrated  by  means  of  a  diagram  (see  Fig.  105). 

In  A  we  have  a  riser  carried  to  the  third  story,  and  from  there  a 
drop  brought  down  to  supply  a  radiator  on  the  first  floor.  The 
elevation  available  for  producing  a  flow  in  the  riser  is  only  10  feet, 
the  same  as  though  it  extended  only  to  the  radiator.  The  water  in 
the  two  pipes  above  the  radiator  is  practically  at  the  same  temperature, 
and  therefore  in  equilibrium,  and  has  no  effect  on  the  flow  of  the 
water  in  the  riser.  (Actually  there  would  be  some  radiation  from  the 
pipes,  and  the  return,  above  the  radiator,  would  be  slightly  cooler,  but 
for  purposes  of  illustration  this  may  be  neglected).  If  the  radiator 
was  on  the  second  floor  the  elevation  of  the  system  would  be  20  feet 
(see  #);  and  on  the  third  floor,  30  feet;  and  so  on.  The  distance 
which  the  pipe  is  carried  above  the  first  radiator  which  it  supplies 
has  but  little  effect  in  producing  a  flow,  especially  if  covered,  as  it 
should  be  in  practice.  Having  seen  that  the  flow  in  the  main  riser 
depends  upon  the  elevation  of  the  radiators,  it  is  easy  to  see  that  the 
way  in  which  it  is  distributed  on  the  different  floors  must  be  con- 
sidered. For  example,  in  B,  Fig.  105,  there  will  be  a  more  rapid 
flow  through  the  riser  with  the  radiators  as  shown,  than  there  would 
be  if  they  were  reversed  and  the  largest  one  were  placed  upon  the  first 
floor. 

We  get  the  average  elevation  of  the  system  by  multiplying  the 
square  feet  of  radiation  on  each  floor  by  the  elevation  above  the 
heater,  then  adding  these  products  together  and  dividing  the  same 
by  the  total  radiation  in  the  whole  system.  In  the  case  shown  in 
By  the  average  elevation  of  the  system  would  be 
(100  X  30)  +  (50  X  20)  +  (25  X  10)  _ 

100  +  50  +  25 

and  we  must  proportion  the  main  riser  the  same  as  though  the  whole 
radiation  were  on  the  second  floor.  Looking  in  Table  XXVII,  we 
find,  for  the  second  story,  that  a  IJ-inch  pipe  will  supply  140  square 


HEATING  AND  VENTILATION 


113 


feet;  and  a  2-inch  pipe,  275  feet.     Probably  a  H-inch  pipe  would 
be  sufficient. 

Although  the  height  of  stories  varies  in  different  buildings,  10 

feet  will  be  found  sufficiently  accurate  for  ordinary  practice. 

+• 

INDIRECT  HOT=WATER  HEATING 

This  is  used  under  the  same  conditions  as  indirect  steam,  and 
the  heaters  used  are  similar  to  those  already  described.     Special 


100 


50 


A  B 

Fig.  105.    Diagram  to  Illustrate  Finding  of  Average  Elevation  of  Heating  System. 

attention  is  given  to  the  form  of  the  sections,  in  order  that  there  may 
be  an  even  distribution  of  water  through  all  parts  of  them.  As  the 
stacks  are  placed  in  the  basement  of  a  building,  and  only  a  short 
distance  above  the  boiler,  extra  large  pipes  must  be  used  to  secure  a 
proper  circulation,  for  the  head  producing  flow  is  small.  The  stack 


114  HEATING  AND  VENTILATION 

casings,  cold-air  arid  warm-air  pipes,  and  registers  are  the  same  as 
in  steam  heating. 

Types  of  Radiators.  The  radiators  for  indirect  hot-water  heating 
are  of  the  same  general  form  as  those  used  for  steam.  Those  shown 
in  Figs.  52,  53,  56,  106,  and  107  are  common  patterns.  The  drum 
pin,  Fig.  106,  is  an  excellent  form,  as  the  method  of  making  the 
connections  insures  a  uniform  distribution  of  water  through  the 
stack. 

Fig.  107  shows  a  radiator  of  good  form  for  water  circulation,  and 
also  of  good  depth,  which  is  a  necessary  point  in  the  design  of  hot- 
water  radiators.  They  should  be  not  less  than  12  or  15  inches  deep 
for  good  results.  Box  coils  of  the  form  given  for  steam  may  also  be 


Fig.  106.    "Drum  Pin"  Indirect  Hot-Water  Radiator. 

used,  provided  the  connections  for  supply  and  return  are  made  of 
good  size. 

Size  of  Stacks.  As  indirect  hot-water  heaters  are  used  princi- 
pally in  the  warming  of  dwelling-houses,  and  in  combination  with 
direct  radiation,  the  easiest  method  is  to  compute  the  surfaces  required 
for  direct  radiation,  and  multiply  these  results  by  1 .5  for  pin  radiators 
of  good  depth.  For  other  forms  the  factor  should  vary  from  1 . 5 
to  2,  depending  upon  the  depth  and  proportion  of  free  area  for  air- 
flow between  the  sections. 

If  it  is  desired  to  calculate  the  required  surface  directly  by  the 
thermal  unit  method,  we  may  allow  an  efficiency  of  from  360  to  400 
for  good  types  in  zero  weather. 


HEATING  AND  VENTILATION 


115 


In  schoolhouse  and  hospital  work,  where  larger  volumes  of  air 
are  warmed  to  lower  temperatures,  an  efficiency  as  high  as  500  B.  T.  U. 
may  be  allowed  for  radiators  of  good  form. 

Flues  and  Casings.  For  cleanliness,  as  well  as  for  obtaining 
the  best  results,  indirect  stacks  should  be  hung  at  one  side  of  the 
register  or  flue  receiving  the  warm  air,  and  the  cold-air  duct  should 
enter  beneath  the  heater  at  the  other  side.  A  space  of  at  least  10 
inches,  and  preferably  12,  should  be  allowed  for  the  warm  air  above 
the  stack.  The  top  of  the  casing  should  pitch  upward  toward  the 
warm-air  outlet  at  least  an  inch  in  its  length.  A  space  of  from  8  to 
10  inches  should  be  allowed  for  cold  air  below  the  stack. 

As  the  amount  of  air  warmed  per  square  foot  of  heating  surface 
is  less  than  in  the  case  of  steam,  we  may  make  the  flues  somewhat 
smaller  as  compared 
with  the  size  of  heater. 
The  following  p  r  o  - 
portions  may  be  used 
under  usual  conditions 
for  dwelling-houses: 
1J  square  inches  per 
square  foot  of  radia- 
tion for  the  first  floor, 
1J  square  inches  for 
the  second  floor,  and 
1J  square  inches  for 
the  cold-air  duct. 

Pipe  Connections.  In  indirect  hot-water  work,  it  is  not  desirable 
to  supply  more  than  80  to  100  square  feet  of  radiation  from  a  single 
connection.  When  the  requirements  call  for  larger  stacks,  they 
should  be  divided  into  two  or  more  groups  according  to  size. 

It  is  customary  to  carry  up  the  main  from  the  boiler  to  a  point 
near  the  basement  ceiling,  where  it  is  air-vented  through  a  small 
pipe  leading  to  the  expansion  tank.  The  various  branches  should 
grade  downward  and  connect  with  the  tops  of  the  stacks.  In  this 
way,  all  air,  both  from  the  boiler  and  from  the  stacks,  will  find  its  way 
to  the  highest  point  in  the  main,  and  be  carried  off  automatically. 

As  an  additional  precaution,  a  pet-cock  air-valve  should  be  placed 
in  the  last  section  of  each  stack,  and  brought  out  through  the  casing 
by  means  of  a  short  pipe. 


Fig.  107.    Indirect  Hot- Water  Radiator. 


116 


HEATING  AND  VENTILATION 


TABLE  XXVIII 

Radiating  Surface  Supplied  by  Pipes  of  Various  Sizes— Indirect  Hot- 
Water  System 


DIAMETER 


SQUARE  FEET   OP  RADIATING  SURFACE 


PIPE 

100  Ft.  Run 

200  Ft.  Run 

300  Ft.  Run 

400  Ft.  Run 

1     in. 

15 

H 

30 

25 

1* 

50 

40 

25 

2 

100 

75 

60 

50 

2* 

175 

125 

100 

90 

3 

275 

200 

150 

140 

3* 

425 

300 

225 

200 

4 

600 

425 

350 

300 

5 

. 

700 

575 

500 

6 

800 

7 

1,200 

Some  engineers  make  a  practice  of  carrying  the  main  to  the 
ceiling  of  the  first  story,  and  then  dropping  to  the  basement  before 
branching  to  the  stacks,  the  idea  being  to  accelerate  the  flow  of  water 
through  the  main,  which  is  liable  to  be  sluggish  on  account  of  the 
small  difference  in  elevation  between  the  boiler  and  stacks.  If 
the  return  leg  of  the  loop  is  left  uncovered,  there  will  be  a  slight  drop 
in  temperature,  tending  to  produce  this  result;  but  in  any  case  it  will 
be  exceedingly  small.  With  supply  and  return  mains  of  suitable 
size  and  properly  graded,  there  should  be  no  difficulty  in  securing  a 
good  circulation  in  basements  of  average  height. 

Pipe  Sizes.  As  the  difference  in  elevation  between  the  stacks 
and  the  heater  is  necessarily  small,  the  pipes  should  be  of  ample  size 
to  offset  the  slow  velocity  of  flow  through  them.  The  sizes  mentioned 
in  Table  XXVIII,  for  runs  up  to  400  feet,  will  be  found  to  supply 
ample  radiating  surface  for  ordinary  conditions.  Some  engineers 
make  a  practice  of  using  somewhat  smaller  pipes,  but  the  larger  sizes 
will  in  general  be  found  more  satisfactory. 

CARE  AND  MANAGEMENT  OF  HOT=WATER  HEATERS 

The  directions  given  for  the  care  of  steam-heating  boilers  apply 
in  a  general  way  to  hot-water  heaters,  as  to  the  methods  of  caring 
for  the  fires  and  for  cleaning  and  filling  the  heater.  Only  the  special 
points  of  difference  need  be  considered.  Before  building  the  fire,  all 
the  pipes  and  radiators  must  be  full  of  water,  and  the  expansion  tank 


HEATING  AND  VENTILATION 


117 


should  be  partially  filled  as  indicated  by  the  gauge-glass.  Should 
the  water  in  any  of  the  radiators  fail  to  circulate,  see  that  the  valves 
are  wide  open  and  that  the  radiator  is  free  from  air.  Water  must 
always  be  added  at  the  expansion  tank  when  for  any  reason  it  is 
drawn  from  the  systeih. 

The  required  temperature  of  the  water  will  depend  upon  the 
outside  conditions,  and  only  enough  fire  should  be  carried  to  keep 
the  rooms  comfortably  warm.  Ther- 
mometers should  be  placed  in  the  flow 
and  return  pipes  near  the  heater,  as  a 
guide.  Special  forms  are  made  for 
this  purpose,  in  which  the  bulb  is  im- 
mersed in  a  bath  of  oil  or  mercury  (see 
Fig.  108). 


FORCED 


HOT-WATER 
LATION 


CIRCU- 


While  the  gravity  system  of  hot- 
water  heating  is  well  adapted  to 
buildings  of  small  and  medium  size, 
there  is  a  limit  to  which  it  can  be  car- 
ried economically.  This  is  due  to  the 
slow  movement  of  the  water,  which 
calls  for  pipes  of  excessive  size.  To 
overcome  this  difficulty,  pumps  are 
used  to  force  the  water  through  the 
mains  at  a  comparatively  high  velocity. 

The  water  may  be  heated  in  a 
boiler  in  the  same  manner  as  for 
gravity  circulation,  or  exhaust  steam 
may  be  utilized  in  a  feed-water  heater 

»  !  .  p,  »     , 

of  large  size.     Sometimes  part  of  the 

heat  is  derived  from  an  economizer  placed  in  the  smoke  passage 

from  the  boilers. 

Systems  of  Piping.  The  mains  for^forced  circulation  are  usually 
run  in  one  of  two  ways.  In  the  two-pipe  system,  shown  in  Fig.  109, 
the  supply  and  return  are  carried  side  by  side,  the  former  reducing 
in  size,  and  the  latter  increasing  as  the  branches  are  taken  off. 


mine  Temperature  of  Water. 


118 


HEATING~AND  VENTILATION 


The  flow  through  the  risers  is  produced  by  the  difference  in 
pressure  in  the  supply  and  return  mains;  and  as  this  is  greatest 
nearest  the  pump,  it  is  necessary  to  place  throttle-valves  in  the  risers 
to  prevent  short-circuiting  and  to  secure  an  even  distribution  through 
all  parts  of  the  system. 

Fig.  110  shows  the  single-pipe  or  circuit  system.  This  is  similar 
to  the  one  already  described  for  gravity  circulation,  except  that  it  can 
be  used  on  a  much  larger  scale. 

A  single  main  is  carried  entirely  around  the  building  in  this 
case,  the  ends  being  connected  with  the  suction  and  discharge  of  the 
pump  as  shown. 

As  the  pressure  or  head  in  the  main  drops  constantly  throughout 
the  circuit,  from  the  discharge  of  the  pump  back  to  the  suction,  it  is 


Fig.  109.    "Two-Pipe"  System  for  Forced  Hot- Water  Circulation. 


evident  that  if  a  supply  riser  be  taken  off  at  any  point,  and  the  return 
be  connected  into  the  main  a  short  distance  along  the  line,  there  will 
be  a  sufficient  difference  in  pressure  between  the  two  points  to  produce 
a  circulation  through  the  two  risers  and  the  connecting  radiators, 
A  distance  of  8  or  10  feet  between  the  connections  is  usually  ample  to 
produce  the  necessary  circulation,  and  even  less  if  the  supply  is  taken 
from  the  top  of  the  main  and  the  return  connected  into  the  side. 

Sizes  of  Mains  and  Branches.  As  the  velocity  of  flow  is  inde- 
pendent of  the  temperature  and  elevation  when  a  pump  is  used,  it  is 
necessary  to  consider  only  the  volume  of  water  to  be  moved  and  the, 
length  of  run. 


HEATING  AND  VENTILATION 


119 


The  volume  is  found  by  the  equation 


500  T' 
in  which 

Q  =  Gallons  of  water  required  per  minute; 
R  —  Square  feet'of  radiating  surface  to  be  supplied; 
E  =  Efficiency  of  radiating  surface  in  B.  T.  U.  per  sq.  foot  per  hour; 
T  =  Drop  in  temperature  of  the  water  in  passing  through  the  heating 
system. 

In  systems  of  this  kind,  where  the  circulation  is  comparatively 
rapid,  it  is  customary  to  assume  a  drop  in  temperature  of  30°  to  40°, 
between  the  supply  and  return. 

Having  determined  the  gallons  of  water  to  be  moved,  the  required 
size  of  main  can  be  found  by  assuming  the  velocity  of  flow,  which 
for  pipes  from  5  to  8  inches  in  diameter  may  be  taken  at  400  to  500 


Fig.  110.    "Single-Pipe"  or  "Circuit"  System  for  Forced  Hot- Water  Circulation. 

feet  per  minute.  A  velocity  as  high  as  600  feet  is  sometimes  allowed 
for  pipes  of  large  size,  while  the  velocity  in  those  of  smaller  diameter 
should  be  proportionally  reduced  to  250  or  300  feet  for  a  3-inch  pipe. 
The  next  step  is  to  find  the  pressure  or  head  necessary  to  force  the 
water  through  the  main  at  the  given  velocity.  This  in  general  should 
not  exceed  50  or  60  feet,  and  much  better  pump  efficiencies  will  be 
obtained  with  heads  not  exceeding  35  or  40  feet. 

As  the  water  in  a  heating  system  is  in  a  state  of  equilibrium,  the 
only  power  necessary  to  produce  a  circulation  is  that  required  to 
overcome  the  friction  in  the  pipes  and  radiators;  and,  as  the  area  of 
the  passageways  through  the  latter  is  usually  large  in  comparison 
with  the  former,  it  is  customary  to  consider  only  the  head  necessary 
to  force  the  water  through  the  mains,  taking  into  consideration  the 
additional  friction  produced  by  valves  and  fittings. 


120  HEATING  AND  VENTILATION 

Each  long-turn  elbow  may  be  taken  as  adding  about  4  feet  to 
the  length  of  pipe;  a  short-turn  fitting,  about  9  feet;  6-inch  and 
4-inch  swing  check-valves,  50  feet  and  25  feet,  respectively;  and 
6-inch  and  4-inch  globe  check-valves,  200  feet  and  130  feet,  respec- 
tively. 

Table  XXIX  is  prepared  especially  for  determining  the  size  of 
mains  for  different  conditions,  and  is  used  as  follows : 

Example.  Suppose  that  a  heating  system  requires  the  circulation  of  480 
gallons  of  water  per  minute  through  a  circuit  main  600  feet  in  length.  The 
pipe  contains  12  long-turn  elbows  and  1  swing  check-valve.  What  diameter 
of  main  should  be  used  ? 

Assuming  a  velocity  of  480  feet  per  minute  as  a  trial  velocity,  we 
follow  along  the  line  corresponding  to  that  velocity,  and  find  that  a 
5-inch  pipe  will  deliver  the  required  volume  of  water  under  a  head 
of  4.9  feet  for  each  100  feet  length  of  run. 

The  actual  length  of  the  main,  including  the  equivalent  of  the 
fittings  as  additional  length,  is 

600+  (12X9) +  50 -758  feet; 

hence  the  total  head  required  is  4.9  X  7.58  =  37  feet.  As  both 
the  assumed  velocity  and  the  necessary  head  come  within  practicable 
limits,  this  is  the  size  of  pipe  which  would  probably  be  used.  If  it 
were  desired  to  reduce  the  power  for  running  the  pump,  the  size  of 
main  could  be  increased.  That  is,  Table  XXIX  shows  that  a  6-inch 
pipe  would  deliver  the  same  volume  of  water  with  a  friction  head  of 
only  about  2  feet  per  100  feet  in  length,  or  a  total  head  of  2  X  7 .58  = 
15  feet. 

The  risers  in  the  circuit  system  are  usually  made  the  same  size 
as  for  gravity  work,  With  double  mains,  as  shown  in  Fig.  109,  they 
may  be  somewhat  smaller,  a  reduction  of  one  size  for  diameters  over 
1J  inches  being  common 

The  branches  connecting  the  risers  with  the  mains  may  be  pro- 
portioned from  the  combined  areas  of  the  risers.  When  the  branches 
are  of  considerable  size,  the  diameter  may  be  computed  from  the 
available  head  and  volume  of  water  to  be  moved. 

Pumps.  Centrifugal  pumps  are  usually  employed  in  connection 
with  forced  hot-water  circulation,  in  preference  to  pumps  of  the 
piston  or  plunger  type.  They  are  simple  in  construction,  having 
no  valves,  produce  a  continuous  flow  of  water,  and,  for  the  low  heads 


HEATING  AND  VENTILATION 


121 


TABLE  XXIX 

Capacity  in  Gallons  per  Minute  Discharged  at  Velocities  of  300  to  540  Feet  per  Minute  —  Also  Friction  Head  in 
Feet,  per  100  Feet  Length  of  Pipe 

DIAMETER  OF  PIPE 

8-lNCH 

Friction 

H 

CO 

<M 

00 

CO 

Capacity 

CO 

R 

CO 

o 

l-H 

i—  r 

a 
u 
fc 

2 

Friction 

CO 

l-H 

CO 

5 

Capacity 

o 

Oi 

Oi 

6-1  NCH 

Friction 

l-H 

8 

O5 

o 
10 

Capacity 

0 

U5 

8 

O5 

a 

0 

Friction 

8 

OS 

l-H 

l-H 

CO 

"o 
0 

s 

o 

O5 

1 

4-1  NCH 

Friction 

<N 

<N 

l-H 

CO 

CO 

1 

8 

O5 

co 

<N 

10 
CO 

3-lNCH 

Friction 

i-H 

CO 

CO 
oo 

0 

1 

ft 

8 

o 

l-H 

l-H 

§ 

Velocity 

o 

o 

00 

o 

122  HEATING  AND  VENTILATION 

against  which  they  are  operated,  have  a  good  efficiency.  A  pump  of 
this  type,  with  a  direct-connected  engine,  is  shown  in  Fig.  111. 

Under  ordinary  conditions  the  efficiency  of  a  centrifugal  pump 
falls  off  considerably  for  heads  above  30  or  35  feet;  but  special  high- 
speed pumps  are  constructed  which  work  with  a  good  efficiency 
against  500  feet  or  more. 

Under  favorable  conditions  an  efficiency  of  60  to  70  per  cent  is 
often  obtained;  but  for  hot-water  circulation  it  is  more  common  to 
assume  an- efficiency  of  about  50  per  cent  for  the  average  case. 

The  horse-power  required  for  driving  a  pump  is  given  by  the 
following  formula: 

TT  p  _HxVX  8.3 
''    33,000  XE' 

in  which 

H  =  Friction  head  in  feet; 

V  =  Gallons  of  water  delivered  per  minute; 

E  =  Efficiency  of  pump. 

Centrifugal  pumps  are  made  in  many  sizes  and  with  varying 
proportions,  to  meet  the  different  requirements  of  capacity  and  head. 

Heaters.  If  the  water  is  heated  in  a  boiler,  any  good  form  may 
be  used,  the  same  as  for  gravity  work.  In  case  tubular  boilers  are 
used,  the  entire  shell  may  be  filled  with  tubes,  as  no  steam  space  is 
required. 

In  order  to  prevent  the  water  from  passing  in  a  direct  line  from 
the  inlet  to  the  outlet,  a  series  of  baffle-plates  should  be  used  to  bring 
it  in  contact  with  all  parts  of  the  heating  surface. 

When  steam  is  used  for  heating  the  water,  it  is  customary  to 
employ  a  closed  feed-water  heater  with  the  steam  on  the  inside  of  the 
tubes  and  the  water  on  the  outside. 

Any  good  form  of  heater  can  be  used  for  this  purpose  by  providing 
it  with  steam  connections  of  sufficient  size.  In  the  ordinary  form  of 
heater,  the  feed-water  flows  through  the  tubes,  and  the  connections 
are  therefore  small,  making  it  necessary  to  substitute  special  nozzles 
of  large  size  when  used  in  the  manner  here  described. 

When  computing  the  required  amount  of  heating  surface  in  the 
tubes  of  a  heater,  it  is  customary  to  assume  an  efficiency  of  about  200 
B.  T.  U.  per  square  foot  of  surface  per  hour,  per  degree  difference  in 
temperature  between  the  water  and  steam. 


HEATING  AND  VENTILATION 


123 


It  is  usual  to  circulate  the  water  at  a  somewhat  higher  tempera- 
ture in  systems  of  this  kind,  and  a  maximum  initial  temperature  of 
200  degrees,  with  a  drop  of  40  degrees  in  the  heating  system,  may  be 
used  in  computing  the  size  of  heater.  If  exhaust  steam  is  used  at 
atmospheric  pressure,  there  will  be  a  difference  of  212  --  180  =  32 
degrees,  between  the  average  temperature  of  the  water  and  the  steam , 
giving  an  efficiency  of  200  X  32  =  6,400  B.  T.  U.  per  square  foot 
of  heating  surface. 

From  this  it  is  evident  that  6,400  -r-  170  ==  38  square  feet  of 
direct  radiating  surface,  or  6,400  —  400  =16  square  feet  of  indirect, 
may  be  supplied  from  each  square  foot  of  tube  surface  in  the  heater. 

Example.  A  building  having  6,000  square  feet  of  direct,  and  2,000 
square  feet  of  indirect  radiation-,  is  to  be  warmed  by  hot  water  under  forced 
circulation.  Steam  at  atmospheric  pressure  is  to  be  used  for  heating  the 
water.  Haw  many  square  feet  of  heating  surface  should  the  heater  contain  ? 

6,000  -7- 38  =158;  and  2,000 
-T-  16  =  125;  therefore,  158  + 
125  =  283  square  feet,  the  area 
of  heating  surface  called  for. 

When  the  exhaust  steam  is 
not  sufficient  for  the  require- 
ments, an  auxiliary  live  steam 
heater  is  used  in  connection 
with  it. 

EXAMPLES  FOR  PRACTICE 

1.  A   building   contains 
10,000    square     feet     of    direct 
radiation  and  4,000  square   feet 
of     indirect     radiation.       How 

many  gallons  of  water  must  be  circulated  through  the  mains  per  min- 
ute, allowing  a  drop  in  temperature  of  40  degrees?  ANS.  165  gal. 

2.  In  the  above  example,  what  size  of  main  should   be   used, 
assuming  the  circuit  to  be  300  feet  in  length  and  to  contain  ten  long- 
turn  elbows?     The  friction  head  is  not  to  exceed  10  ft.,  and  the 
velocity  of  flow  not  to  exceed  300  feet  per  minute.    ANS.  4-inch. 

3.  What  horse-power  will  be   required   to  drive  a  centrifugal 
pump  delivering  400  gallons  per  minute  against  a  friction  head  of 
40  feet,  assuming  an  efficiency  of  50  per  cent  for  the  pump? 

ANS.  8  H.  P. 


Fig.  111.     Centrifugal   Pump  Direct-Con- 
nected to  Engine,  for  Forced  Hot- 
Water  Circulation. 


124  HEATING  AND  VENTILATION 

4.  A  building  contains  10,000  square  feet  of  direct  radiation  and 
5,000  square  feet  of  indirect  radiation.     Steam  at  atmospheric  pres- 
sure is  to  be  used.     The  initial  temperature  of  the  water  is  to  be  200°; 
and  the  final  P  160°.     How  many  square  feet  of  heating  surface  should 
the  heater  contain?  ANS.  575  sq.  ft. 

5.  How  many  square  feet  would  be  required  in  the  above 
heater  (Example  4)  if  the  initial  temperature  of  the  water  were  180° 
and  the  final  temperature  150°?  ANS.  399  sq.  ft. 

EXHAUST-STEAM  HEATING 

Steam,  after  being  used  in  an  engine,  contains  the  greater  part 
of  its  heat;  and  if  not  condensed  or  used  for  other  purposes,  it  can 
usually  be  employed  for  heating  without  affecting  to  any  great  extent 
the  power  of  the  engine.  In  general,  we  may  say  that  it  is  a  matter  of 
economy  to  use  the  exhaust  for  heating,  although  various  factors 
must  be  considered  in  each  case  to  determine  to  what  extent  this  is 
true.  The  more  important  considerations  bearing  upon  the  matter 
are:  the  relative  quantities  of  steam  required  for  power  and  for 
heating;  the  length  of  the  heating  season;  the  type  of  engine  used; 
the  pressure  carried;  and,  finally,  whether  the  plant  under  con- 
sideration is  entirely  new,  or  whether,  on  the  other  hand,  it  involves 
the  adapting  of  an  old  heating  system  to  a  new  plant. 

The  first  use  to  be  made  of  the  exhaust  steam  is  the  heating  of 
the  feed-water,  as  this  effects  a  constant  saving  both  summer  and 
winter,  and  can  be  done  without  materially  increasing  the  back- 
pressure on  the  engine.  Under  ordinary  conditions,  about  one-sixth 
of  the  steam  supplied  to  the  engine  can  be  used  in  this  way,  or  more 
nearly  one-fifth  of  the  exhaust  discharged  from  the  engine. 

We  may  assume  in  average  practice  that  about  80  per  cent  of 
the  steam  supplied  to  an  engine  is  discharged  in  the  form  of  steam 
at  a  lower  pressure,  the  remaining  20  per  cent  being  partly  converted 
into  work  and  partly  lost  through  cylinder  condensation.  Taking 
this  into  account,  there  remains,  after  deducting  the  steam  used  for 
feed-water  heating,  .8  X  |-  =  .64  of  the  entire  quantity  of  steam 
supplied  to  the  engine,  available  for  heating  purposes. 

When  the  quantity  of  steam  required  for  heating  is  small  com- 
pared with  the  total  amount  supplied  to  the  engine,  or  where  the 
heating  season  is  short,  it  is  often  more  economical  to  run  the  engine 


HEATING  AND  VENTILATION  125 

condensing  and  use  the  live  steam  for  heating.  This  can  be  deter- 
mined in  any  particular  case  by  computing  the  saving  in  fuel  by  the 
use  of  a  condenser,  taking  into  account  the  interest  and  depreciation 
on  the  first  cost  of  the  condensing  apparatus,  and  the  cost  of  water, 
if  it  must  be  purchased,  and  comparing  it  with  the  cost  of  heating 
with  live  steam. 

Usually,  however,  in  the  case  of  office  buildings  and  institutions, 
and  commonly  in  the  case  of  shops  and  factories,  especially  in  north- 
erly latitudes,  it  is  advantageous  to  use  the'exhaust  forjieating,  even  if 
a  condenser  is  installed  for  summer  use  only.  The  principal  objec- 
tion raised  to  the  use  of  exhaust  steam  has  been  the  higher  back- 
pressure required  on  the  engines,  resulting  in  a  loss  of  power  nearly 
proportional  to  the  ratio  of  the  back-pressure  to  the  mean  effective 
pressure.  There  are  two  ways  of  offsetting  this  loss — one,  by  raising 
the  initial  or  boiler  pressure;  and  the  other,  by  increasing  the  cut- 
off of  the  engine.  Engines  are  usually  designed  to  work  most  econom- 
ically at  a  given  cut-off,  so  that  in  most  cases  it  is  undesirable  to 
change  it  to  any  extent.  -Raising  the  boiler  pressure,  on  the  other 
hand,  is  not  so  objectionable  if  the  increase  amounts  to  only  a  few 
pounds. 

Under  ordinary  conditions  in  the  case  of  a  simple  engine,  a  rise 
of  3  pounds  in  the  back-pressure  calls  for  an  increase  of  about  5 
pounds  in  the  boiler  pressure,  to  maintain  the  same  power  at  the 
engine. 

The  indicator  card  shows  a  back-pressure  of  about  2  pounds 
when  an  engine  is  exhausting  into  the  atmosphere,  so  that  an  increase 
of  3  pounds  would  bring  the  pressure  up  to  a  total  of  5  pounds  which 
should  be  more  than  sufficient  to  circulate  the  steam  through  any 
well-designed  heating  system. 

If  it  is  desired  to  reduce  rather  than  increase  the  back-pressure, 
one  of  the  so-called  vacuum  systems,  described  later,  can  be  used. 

The  systems  of  steam  heating  which  have  been  described  are 
those  in  which  the  water  of  condensation  flows  back  into  the  boiler 
by  gravity.  Where  exhaust  steam  is  used,  the  pressure  is  much  below 
that  of  the  boiler,  and  it  must  be  returned  either  by  a  pump  or  by  a 
return  trap.  The  exhaust  steam  is  often  insufficient  to  supply  the 
entire  heating  system,  and  must  be  supplemented  by  live  steam  taken 
directly  from  the  boiler.  This  must  first  pass  through  a  reducing 


126  HEATING  AND  VENTILATION 

valve  in  order  to  reduce  the  pressure  to  correspond  with  that  carried 
in  the  heating  system. 

An  engine  does  not  deliver  steam  continuously,  but  at  regular 
intervals,  at  the  end  of  each  stroke ;  and  the  amount  is  likely  to  vary 
with  the  work  done,  since  the  governor  is  adjusted  to  admit  steam  in 
such  a  quantity  as  is  required  to  maintain  a  uniform  speed.  If  the 
work  is  light,  very  little  steam  will  be  admitted  to  the  engine;  and 
for  this  reason  the  supply  available  for  heating  may  vary  somewhat, 
depending  upon  the  use  made  of  the  power  delivered  by  the  engine. 
In  mills  the  amount  of  exhaust  steam  is  practically  constant;  in 
office  buildings  where  power  is  used  for  lighting,  the  variation  is 
greater,  especially  if  power  is  also  required  for  the  running  of  elevators. 

The  general  requirements  for  a  successful  system  of  exhaust 
steam  heating  include  a  system  of  piping  of  such  proportions  that 
only  a  slight  increase  in  back-pressure  will  be  thrown  upon  the  engine; 
a  connection  which  shall  automatically  supply  live  steam  at  a  reduced 
pressure  as  needed;  provision  for  removing  the  oil  from  the  exhaust 
steam ;  a  relief  or  back-pressure  valve  arranged  to  prevent  any  sudden 
increase  in  back  pressure  on  the  engine;  and  a  return  system  of  some 
kind  for  returning  the  water  of  condensation  to  the  boiler  against 
a  higher  pressure.  These  requirements  may  be  met  in  various  ways, 
depending  upon  actual  conditions  found  in  different  cases. 

To  prevent  sudden  changes  in  the  back-pressure,  due  to  irregular 
supply  of  steam,  the  exhaust  pipe  from  the  engine  is  often  carried  to 
a  closed  tank  having  a  capacity  from  30  to  40  times  that  of  the  engine 
cylinder.  This  tank  may  be  provided  with  baffle-plates  or  other 
arrangements  and  may  serve  as  a  separator  for  removing  the  oil  from 
the  steam  as  it  passes  through. 

Any  system  of  piping  may  be  used;  but  great  care  should  be 
taken  that  as  little  resistance  as  possible  is  introduced  at  bends  and 
fittings ;  and  the  mains  and  branches  should  be  of  ample  size.  Usually 
the  best  results  are  obtained  from  the  system  in  which  the  main  steam 
pipe  is  carried  directly  to  the  top  of  the  building,  the  distributing  pipes 
being  run  from  that  point,  and  the  radiating  surfaces  supplied  by  a 
down-flowing  current  of  steam. 

Before  taking  up  the  matter  of  piping  in  detail  a  few  of  the  more 
important  pieces  of  apparatus  will  be  described  in  a  brief  way. 

Reducing  Valves.    The  action  of  pressure-reducing  valves  has 


HEATING  AND  VENTILATION 


127 


been  taken  up  quite  fully  in  "Boiler  Accessories,"  and  need  not  be 
repeated  here.  When  the  reduction  in  pressure  is  large,  as  in  the 
case  of  a  combined  power  and  heating  plant,  the  valve  may  be  one  or 
two  sizes  smaller  than  the  low-pressure  main  into  which  it  discharges. 
For  example,  a  5-incfi  valve  will  supply  an  8-inch  main,  a  4-inch  a 
6-inch  main,  a  3-inch  a  5-inch  main,  a  2  J-inch  a  4-inch  main,  etc. 

For  the  smaller  sizes,  the  difference  should  not  be  more  than  one 
size.  All  reducing  valves  should  be  provided  with  a  valved  by-pass 
for  cutting  out  the  valvfe  in  case  of  repairs.  This  connection  is  usually 
made  as  shown  in  plan  by  Fig.  112. 

Grease  Extractor.  When  exhaust  steam  is  used  for  heating  pur- 
poses, it  must  first  be  passed  through  some  form  of  separator  for 
removing  the  oil ;  and  as  an  additional  precaution  it  is  well  to  pass  the 

REDUC/NG  (VALVE 


BY-PASS 

Fig.  112.    Connections  of  Reducing  Valve  in  Exhaust-Steam  Heating  System. 

water  of  condensation  through  a  separating  tank  before  returning  it  to 
the  boilers. 

Such  an  arrangement  is  shown  in  Fig.  113.  As  the  oil  collects 
on  the  surface  of  the  water  in  the  tank,  it  can  be  made  to  overflow 
into  the  sewer  by  closing  the  valve  in  the  connection  with  the  receiving 
tank,  for  a  short  time. 

As  much  of  the  oil  as  possible  should  be  removed  before  the 
steam  enters  the  pipes  and  radiators,  else  a  coating  will  be  formed  on 
their  inner  surfaces,  which  will  reduce  their  heating  efficiency.  The 
separation  of  the  oil  is  usually  effected  by  introducing  a  series  of 
baffling  plates  in  the  path  of  the  steam;  the  particles  of  oil  striking 
these  are  stopped,  and  thus  separated  from  the  steam.  The  oil  drops 
into  a  receiver  provided  for  this  purpose  and  is  discharged  through  a 
trap  to  the  sewer. 

In  the  separator,  or  extractor,  shown  in  Fig.  114,  the  separation  is 
accomplished  by  a  series  of  plates  placed  in  a  vertical  position  in  the 


128 


HEATING  AND  VENTILATION 


body  of  the  separator,  through  which  the  steam  must  pass.  These 
plates  consist  of  upright  hollow  columns,  with  openings  at  regular 
intervals  for  the  admission  of  water  and  oil,  which  drain  downward 
to  the  receiver  below.  The  steam  takes  a  zigzag  course,  and  all  of 
it  comes  in  contact  with  the  intercepting  plates,  which  insures  a 
thorough  separation  of  the  oil  and  other  solid  matter  from  the  steam. 
Another  form,  shown  in  Fig.  115,  gives  excellent  results,  and  has  the 
advantage  of  providing  an  equalizing  chamber  for  overcoming,  to 
some  extent,  the  unequal  pressure  due  to  the  varying  load  on  the 
engine.  It  consists  of  a  tank  or  receiver  about  4  feet  in  diameter, 
with  heavy  boiler-iron  heads  slightly  crowned  to  give  stiffness. 


Water — line  in 
Receiving  TanT< 

"^=£ 


jJTo  Sewer 
To  ReeeivingTank 


Fig.  113.    Separator  for  Removing  Oil  from  Exhaust  Steam  and  Water  Condensation. 

Through  the  center  is  a  layer  of  excelsior  (wooden  shavings  of  long 
fibre)  about  12  inches  in  thickness,  supported  on  an  iron  grating, 
with  a  similar  grating  laid  over  the  top  to  hold  it  in  place.  The 
steam  enters  the  space  below  the  excelsior  and  passes  upward,  as 
shown  by  the  arrows.  The  oil  is  caught  by  the  excelsior,  which  can 
be  renewed  from  time  to  time  as  it  becomes  saturated.  The  oil  and 
water  which  fall  to  the  bottom  of  the  receiver  are  carried  off  through 
a  trap.  Live  steam  may  be  admitted  through  a  reducing  valve,  for 
supplementing  the  exhaust  when  necessary. 

Back=Pressure  Valve.  This  is  a  form  of  relief  valve  which  is 
placed  in  the  outboard  exhaust  pipe  to  prevent  the  pressure  in  the 
heating  system  from  rising  above  a  given  point.  Its  office  is  the 


HEATING  AND  VENTILATION 


129 


reverse  of  the  reducing  valve,  which  supplies  more  steam  when 
the  pressure  becomes  too  low.  The  form  shown  in  Fig.  116  is 
designed  for  a  vertical  pipe.  The  valve  proper  consists  of  two  discs 
of  unequal  area,  the  combined  area  of  which  equals  that  of  the  pipe. 
The  force  tending  to  open  the  valve  is  that  due  to  the  steam  pressure 
acting  on  ait  area  equal  to  the  difference  in  area  between  the  two  discs; 
it  is  clear  from  the  cut  that  the 
pressure  acting  on  the  larger 
disc  tends  to  open  the  valve 
while  the  pressure  on  the  smal- 
ler acts  in  the  opposite  direc- 
tion. The  valve-stem  is  con- 
nected by  a  link  and  crank 
arm  with  a  spindle  upon  which 
is  a  lever  and  weight  outs'ide. 
As  the  valve  opens,  the  weight 
is  raised,  so  that,  by  placing  it 
in  different  positions  on  the 
lever  arm,  the  valve  will  open 
at  any  desired  pressure. 

Fig.  117  shows  a  different 
type,  in  which  a  spring  is  used 
instead  of  a  weight.  This 
valve  has  a  single  disc  moving  RECEIVER 
in  a  vertical  direction.  The 
valve  stem  is  in  the  form  of  a 
piston  or  dash-pot  which  pre- 
vents a  too  sudden  movement 
and  makes  it  more  quiet  in 
its  action.  The  disc  is  held 
on  its  seat  against  the  steam 
pressure  by  a  lever  attached 
to  the  spring  as  shown.  When 
the  pressure  of  the  steam  on  the  underside  becomes  greater  than  the 
tension  of  the  spring,  the  valve  lifts  and  allows  the  steam  to  escape. 
The  tension  of  the  spring  can  be  varied  by  means  of  the  adjusting 
screw  at  its  upper  end. 

A  back-pressure  valve   is  simply  a  low-pressure  safety-valve 


DISCHARGE 


Fig.  114.    Oil  Separator  Consisting  of  Vertical 

Plates  with  Openings  Giving  Steam  a 

Zigzag  Course. 


130 


HEATING  AND  VENTILATION 


designed  with  a  specially  large  opening  for  the  passage  of  steam 
through  it.  These  valves  are  made  for  horizontal  as  well  as  for 
vertical  pipes. 


MANt-fOLC 


STEAM   ft~ 
FROM  REDUCING 
VALVE 


EXHAUST f 

FROM  ENG/NE 


EXCELS/OR  /STRAINER 


5  TEAM  TO 

HEATING 

SYSTEM 


^HANDHOLE 


D 


TO  TRAP 


Fig.  115.    Oil  Separator  Consisting  of  a  Tank  in  which  Steam  is  Filtered  by  Passing 
Upward  through  a  Liayer  of  Excelsior. 

Exhaust  Head.  This  is  a  form  of  separator  placed  at  the  top 
of  an  outboard  exhaust  pipe  to  prevent  the  water  carried  up  in  the 
steam  from  falling  upon  the  roofs  of  buildings  or  in  the  street  below. 
Fig.  118  is  known  as  a  centrifugal  exhaust  head.  The  steam,  on 

entering  at  the  bottom,  is  given  a 
whirling  or  rotary  motion  by  the 
spiral  deflectors;  and  the  water  is 
thrown  outward  by  centrifugal  force 
against  the  sides  of  the  chamber,  from 
which  it  flows  into  the  shallow  trough 
at  the  base,  and  is  carried  away  through 
the  drip-pipe,  which  is  brought  down 
and  connected  with  a  drain-pipe  in- 
side the  building.  The  passage  of  the 
steam  outboard  is  shown  by  the  arrows. 


Fig.  116.    Automatically  Acting  Back-     „  ,  „  ,  .  ,  .   ,        , 

Pressure  Valve  Attached  to  ver-      Other  lorms   are   used  in  which  the 

tical  Pipe.      For  Preventing 

water  is  separated  from  the  steam  by 


Rise  of  Pressure  in  System 

above  ah-y   Desired 

Point. 


deflectors  which  change  the  direction  of 

the  currents. 

Automatic  Return=Pumps.  '  In  exhaust  heating  plants,  the 
condensation  is  returned  to  the  boilers  by  means  of  some  form  of 
return-pump.  A  combined  pump  and  receiver  of  the  form  illus- 


HEATING  AND  VENTILATION 


131 


trated  in  Fig.  119  is  generally  used.  This  consists  of  a  cast-iron  or 
wrought-iron  tank  mounted  on  a  base  in  connection  with  a  boiler 
feed-pump.  Inside  the  tank  is  a  ball-float  connected  by  means  of 
levers  with  a  valve  in  the  steam  pipe  which  is  connected  with  the 
pump.  When  the  water-line  in  the  tank  rises  above  a  certain  level, 
the  float  is  raised  and  opens  the  steam  valve,  which  starts  the  pump. 
When  the  water  is  lowered  to  its  normal  level,  the  valve  closes  and 
the  pump  stops.  By  this  arrangement,  a  constant  water-line  is 
maintained  in  the  receiver,  and  the  pump  runs  only  as  needed  to  care 
for  the  condensation  as  it  returns  from  the  heating  system.  If  dry 
returns  are  used,  they  may  be  brought  together  and  connected  with 
the  top  of  the  receiver.  If  it  is  desired  to  seal  the  horizontal  runs,  as 


Fig.  117.    Back-Pressure  Valve  Automatic- 
ally Operated  by  a  Spring. 


Fig.  118.    Centrifugal  Exhaust  Head. 


is  usually  the  case,  the  receiver  may  be  raised  to  a  height  sufficient 
to  give  the  required  elevation  and  the  returns  connected  near  the 
bottom  below  the  water-line. 

A  balance-pipe,  so  called,  should  connect  the  heating  main  with 
the  top  of  the  tank,  for  equalizing  the  pressure;  otherwise  the  steam 
above  the  water  would  condense,  and  the  vacuum  thus  formed  would 
draw  all  the  water  into  the  tank,  leaving  the  returns  practically  empty 
and  thus  destroying  the  condition  sought.  Sometimes  an  inde- 
pendent regulator  or  pump  governor  is  used  in  place  of  a  receiver. 
One  type  is  shown  in  Fig.  120.  The  return  main  is  connected  at 


132 


HEATING  AND  VENTILATION 


the  upper  opening,  and  the  pump  suction  at  the  lower.  A  float  inside 
the  chamber  operates  the  steam  valve  shown  at  the  top,  and  the  pump 
works  automatically  as  in  the  case  just  described. 

If  it  is  desired  to  raise  the  water-line,  the  regulator  may  be 
elevated  to  the  desired  height  and  connections  made  as  shown  in 
Fig.  121. 

Return  Traps.  The  principle  of  the  return  trap  has  been  de- 
scribed in  " Boiler  Accessories,"  but  its  practical  form  and  application 


Fig.  119.    Combined  Receiver  and  Automatic  Pump  for  Returning  Water  of 
Condensation  to  Boiler. 

will  be  taken  up  here.  The  type  shown  in  Fig.  122  has  all  its  working 
parts  outside  the  trap.  It  consists  of  a  cast-iron  bowl  pivoted  at  G  and 
H.  There  is  an  opening  through  G  connecting  with  the  inside  of 
the  bowl.  The  pipe  K  connects  through  C  with  an  interior  pipe 
opening  near  the  top  (see  Fig.  123).  The  pipe  D  connects  with  a 
receiver,  into  which  all  the  returns  are  brought.  A  is  a  check-valve 
allowing  water  to  pass  through  in  the  direction  shown  by  the  arrow. 
E  is  a  pipe  connecting  with  the  boiler  below  the  water-line.  B  is  a 


HEATING  AND  VENTILATION 


133 


check  opening  toward  the  boiler,  and  K,  a  pipe  connected  with  the 
steam  main  or  drum. 

The  action  of  the  trap  is  as  fol- 
lows :  As  the  bowl  fills  with  water  from 
the  receiver,  it  overbalances  the 
weighted  lever  and  drops  to  the  bot- 
tom of  the  ring.  This  opens  the  valve 
C,  and  admits  steam  at  boiler  pres- 
sure to  the  top  of  the  trap.  Being  at 
a  higher  level  the  water  flows  by  grav- 
ity into  the  boiler,  through  the  pipe  E. 
Water  and  steam  are  kept  from  passing 
out  through  D  by  the  check  A. 

TTT1  i  . .     ,     ..      Fig.  120.    Automatic  Float-Operated 

When    the    trap     has    emptied     it-          Pump  Governor  Used  instead 
.  i»     i        i     11         •  •  °f a  Receiver. 

self,  the  weight  of  the  ball  raises  it 

to  the  original  position,  which  movement  closes  the  valve  C  and  opens 
the  small  vent  F.  The  pressure  in  'the  bowl  being  relieved,  water 
flows  in  from  the  receiver  through  D,  until  the  trap  is  filled,  when  the 


A  U  TO  MA  T/C      VA  L  VE 
*  TO    PUMP 


Fig.  isi.    Pump  Regulator  Placed  at  Sufficient  Height  to  Raise  Water-Line  to 
Point  Desired. 

process  is  repeated '.     In  order  to  work  satisfactorily,  the  trap  should 
be  placed  at  least  3  feet  above  the  water-level  in  the  boiler,  and  the 


134 


HEATING  AND  VENTILATION 


pressure  in  the  returns  must  always  be  sufficient  to  raise  the  water 
from  the  receiver  to  the  trap  against  atmospheric  pressure,  which  is 
theoretically  about  1  pound  for  every  2  feet  in  height.  In  practice 
there  will  be  more  or  less  friction  to 
overcome,  and  suitable  adjustments  must 
be  made  for  each  particular  case. 

Fig.  124  shows  another  form  of  trap 
acting  upon  the  same  principle,  except 
that  in  this  case  the  steam  valve  is  oper- 
ated by  a  bucket  or  float  inside  the  trap. 
The  pipe  connections  are  practically  the 
same  as.  with  the  trap  just  described. 

'Return  traps   are   more    commonly 
used  in  smaller  plants  where  it  is  desired  F:g  123  ^tnrn  Trap  with  work- 
to  avoid  the  expense  and  care  of  a  pump. 

Damper=Regulators.  Every  heating  and  every  power  plant 
should  be  provided  with  automatic  means  for  closing  the  dampers 
when  the  steam  pressure  reaches  a  certain  point,  and  for  opening 
them  again  when  the  pressure  drops.  There  are  various  regulators 
designed  for  this  purpose,  a  simple  form  of  which  is  shown  in  Fig.  125. 

Steam  at  boiler  pres- 
sure is  admitted  beneath  a 
diaphragm  which  is  bal- 
anced by  a  weighted  lever. 
When  the  pressure  rises  to  a 
certain  point,  it  raises  the 
lever  slightly  and  opens  a 
valve  which  admits  water 
under  pressure  above  a  dia- 
phragm located  near  the 
smoke-pipe.  This  action 
forces  down  a  lever  con- 
nected by  chains  with  the 

Fig.  123.    Showing  Interior  Detail  of  Return  Trap    damper,    and     closes     it. 

When   the   steam   pressure 

drops,  the  water-valve  is   closed,    and    the   different    parts   of   the 
apparatus  take  their  original  positions. 

Another  form  similar  in  principle  is  shown  in  Fig.  126.     In  this 


TYPICAL    HEATING    INSTALLATION    SHOWING    SECTIONAL    BOILER 
AND    RADIATOR. 

American  Radiator  Company. 


HEATING  AND  VENTILATION 


135 


case  a  piston  is  operated  by  the  water-pressure,  instead  of  a  diaphragm. 
In  both  types  the  pressures  at  which  the  damper  shall  open  and  close 
are  regulated  by  suitable  adjustments  of  the  weights  upon  the  levers. 
Pipe  Connections.  The  method  of  making  the  pipe  connections 
in  any  particular  "oase  will  depend  upon  the  general  arrangement 
of  the  apparatus  and  the  various  conditions.  Fig.  127  illustrates 


EXHAUST 


Fig.  124.    Return  Trap  with  Steam  Valve  Operated  by  Bucket  or  Float  Inside. 

the  general  principles  to  be  followed,  and  by  suitable  changes  may  be 
used  as  a  guide  in  the  design  of  new  systems. 

Steam  first  passes  from  the  boilers  into  a  large  drum  or  header. 
From  this,  a  main,  provided  with  a  shut-off  valve,  is  taken  as  shown ; 
one  branch  is  carried  to  the  engines,  while  another  is  connected  with 
the  heating  system  through  a  reducing  valve  having  a  by-pass  and 
cut-out  valves.  The  exhaust  from  the  engines  connects  with  the  large 
main  over  the  boilers  at  a  point  just  above  the  steam  drum.  The 


136 


HEATING  AND  VENTILATION 


branch  at  the  right  is  carried  outboard  through  a  back-pressure 
valve  which  may  be  set  to  carry  any  desired  pressure  on  the  system. 
The  other  branch  at  the  left  passes  through  an  oil  separator  into  the 
heating  system.  The  connections  between  the  mains  and  radiators 
are  made  in  the  usual  way,  and  the  main  return  is  carried  back  to  the 
return  pump  near  the  floor.  A  false  water-line  or  seal  is  obtained  by 
elevating  the  pump  regulator  as  already  described.  An  equalizing 


Pig.  125.    Simple  Form  of  Automatic  Damper-Regulator,  Operated  by  Lever  Attached  to 
Diaphragm,  for  Closing  Dampers  when  Steam  Pressure  Reaches  a  Certain  Point. 


or  balance  pipe  connects  the  top  of  the  regulator  writh  the  low-pressure 
heating  main,  and  high  pressure  is  supplied  to  the  pump  as  shown. 

A  sight-feed-  lubricator  should  be  placed  in  this  pipe  above  the 
automatic  valve;  and  a  valved  by-pass  should  be  placed  around  the 
regulator,  for  running  the  pump  in  case  of  accident  or  repairs.  The 
oil  separator  should  be  drained  through  a  special  oil  trap  to  a  catch- 
basin  or  to  the  sewer;  and  the  steam  drum  or  any  other  low  points 


HEATING  AND  VENTILATION 


137 


or  pockets  in  the  high-pressure  piping  should  be  dripped  to  the 
return  tank  through  suitable  traps. 

Means  should  be  provided  for  draining  all  parts  of  the  system 
to  the  sewer,  and  all  traps  and  special  apparatus  should  be  by-passed. 
The  return -pump  should  always  be  duplicated  in  a  plant  of  any  size, 
as  a  safeguard  against  accident;  and  the  two  pumps  should  be  run 
alternately,  to  make  sure  that  one  is  always  in  working  order. 


Fig.  126.    Automatic  Damper-Regulator  Operated  by  Piston  Actuated 
by  Water-Pressure. 


One  piece  of  apparatus  not  shown  in  Fig.  127  is  the  feed-water 
heater.  If  all  of  the  exhaust  steam  can  be  utilized  for  heating  pur- 
poses, this  is  not  necessary,  as  the  cold  water  for  feeding  the  boilers 
may  be  discharged  into  the  return  pipe  and  be  pumped  in  with  the 
condensation.  In  summertime,  however,  when  the  heating  plant  is 
not  in  use,  a  feed-water  heater  is  necessary,  as  a  large  amount  of  heat 


138 


HEATING  AND  VENTILATION 


HEATING  AND  VENTILATION  139 

which  would  otherwise  be  wasted  may  be  saved  in  this  way.  The 
connections  will  depend  somewhat  upon  the  form  of  heater  used; 
but  in  general  a  single  connection  with  the  heating  main  inside  the 
back-pressure  valve  is  all  that  is  necessary.  The  condensation  from 
the  heater  should  be  Vapped  to  the  sewer. 


HEATING  AND  VENTILATION 


PART  III 


VACUUM  SYSTEMS 

Low=Pressure  or  Vacuum  Systems.  In  the  systems  of  steam 
heating  which  have  been  described  up  to  this  point,  the  pressure 
carried  has  always  been  above  that  of  the  atmosphere,  and  the  action 
of  gravity  has  been  depended  upon  to  carry  the  water  of  condensation 
back  to  the  boiler  or  receiver;  the  air  in  the  radiators  has  been  forced 
out  through  air-valves  by  the  pressure  of  steam  back  of  it.  Methods 
will  now  be  taken  up  in  which  the  pressure  in  the  heating  system  is 
less  than  the  atmosphere,  and  where 
the  circulation  through  the  radiators  -is 
produced  by  suction  rather  than  by 
pressure.  Systems  of  this  kind  have 
several  advantages  over  the  ordinary 
methods  of  circulation  under  pressure. 
First — no  back-pressure  is  produced 
at  the  engines  when  used  in  connection 
with  exhaust  steam;  but  rather  there 
will  be  a  reduction  of  pressure  due  to 
the  partial  vacuum  existing  in  the  radia- 
tors. Second  —  there  is  a  complete 
removal  of  air  from  the  coils  and 
radiators,  so  that  all  portions  are 
steam-filled  and  available  for  heating 
purposes.  Third — there  is  complete  drainage  through  the  returns, 
especially  those  having  long  horizontal  runs;  and  there  is  absence  of 
water-hammer.  Fourth  —  smaller  return  pipes  may  be  used. 
The  two  older  systems  of  this  kind  in  common  use  are  known  as  the 
Webster  and  Paul  systems;  other  systems  of  recent  introduction  are 
described  in  the  Instruction  Paper  on  Steam  and  Hot-Water  Fitting. 

Webster  System.  This  consists  primarily  of  an  automatic  outlet- 
valve  on  each  coil  and  radiator,  connected  with  some  form  of  suction 
apparatus  such  as  a  pump  or  ejector.  One  type  of  valve  used  is 


Fig.  128,    Air  Outlet- Valve  for  Radi- 
ator, Automatically  Operated  by 
Expansion  and  Contraction 
of  Vulcanite  Stem. 


142 


HEATING  AND  VENTILATION 


Fig.   129.     Thermostat    At- 

tached  to  Angle- Valve  with 

Top  Removed. 


shown  in  section  in  Fig.  128,  which  replaces  the  usual  hand-valve  at 

the  return  end  of  the  radiator.     It  is  similar  in  construction  to  some 

of  the  air-valves  already  described,  consisting  of  a  rubber  or  vulcanite 

stem  closing  against  a  valve  opening  when 

made  to  expand  by  the  presence  of  steam. 

When  water  or  air  fills  the  valve,  the  stem 

contracts    and    allows   it  to  be  sucked  out 

as    shown    by   the    arrows.     A   perforated 

metal   strainer  surrounds   the   stem  or  ex- 

pansion piece,  to  prevent  dirt  and  sediment 

from  clogging  the  valve. 

Fig.  129  shows  the  valve  —  or  thermostat, 

as  it  is  called  —  attached   to    an    ordinary 

angle-valve  with  the  top  removed  ;  and  Fig. 

130  indicates  the  method  of  draining  the 

bottoms  of  risers  or  the  ends  of  mains. 

Fig.  131  shows  another   form    of   this 

valve,  called   a   water-seal  motor.    This  is 

used  under  practically  the  same  conditions 

as  the  one  described  above.     Its  action  is  as  follows  : 

Ordinarily,  the  seal  A  is  down,  and  the  central  tube-valve  is 

resting  upon  the  seat,  closing  the  port  K  and  preventing  direct  com- 

munication between  the  interior  of 
the  motor-body  E  and  the  outlet. 
L.  The  outlet  is  attached  to  a  pipe 
leading  to  a  vacuum-pump,  or 
other  draining  apparatus,  which 
exhausts  the  space  F  above  the  seal 
through  the  annular  space  between 
the  spindle  B  and  the  inside  of  the 
central  tube  G.  The  water  of 

^^^JanoQ^nr,      ai>mimiilatino%    in    thp 
Condensation,     au 

radiator  or  coil,  passes  into  the 
chamber  E,  through  the  inlet  C,  rises  in  the  chamber,  and  seals  the 
space  between  the  seal-shell  A  and  the  sleeve  of  the  bonnet  D.  The 
differential  pressure  thus  created  causes  the  seal  A  to  rise,  lifting  the 
end  of  the  central  tube  off  the  seat,  thus  opening  a  clear  passageway 
for  the  ejection  of  the  water  of  condensation. 


Fig.  130.     Showing  Method  of  Draining 
Bottoms  of  Risers  or  Ends 


HEATING  AND  VENTILATION 


143 


When  all  the  water  of  condensation  has  been  drawn  out  of  the 
radiator,  the  seal  and  tube  are  reseated  by  gravity,  thus  closing  the 
port  K,  preventing  waste  or  loss  of  steam ;  and  the  pressure  is  equal- 
ized above  and  below  the  seal  because  of  the  absence  of  water.  This 
action  is  practically  instantaneous.  When  the  condensation  is  small 
in  quantity,  the  discharge  is  intermittent  and  rapid. 

The  space  between  the  seal  A  and  the  sleeve  of  the  bonnet  D, 
and  the  annular  space  between  the  central  tube  G  and  the  spindle  B, 


Fig.  131.    Water-Seal  Motor. 

form  a  passageway  through  which  the  air  is  continually  withdrawn  by 
the  vacuum  pump  or  other  draining  apparatus. 

The  action  outlined  continues  as  long  as  water  is  present. 

No  adjustment  whatever  is' necessary;  the  motor  is  entirely  auto- 
matic. 

One  special  advantage  claimed  for  this  system  is  that  the  amount 
of  steam  admitted  to  the  radiators  may  be  regulated  to  suit  the  require- 
ments of  outside  temperature;  and  is  possible  without  water- 


144 


HEATING  AND  VENTILATION 


HEATING  AND  VENTILATION  145 

logging  or  hammering.  This  may  be  done  at  will  by  closing  down  on 
the  inlet  supply  to  the  desired  degree.  The  result  is  the  admission 
of  a  smaller  amount  of  steam  to  the  radiator  than  it  is  calculated  to 
condense  normally.  >The  condensation  is  removed  as  fast  as  formed, 
by  the  opening  of  the  thermostatic  valve. 

The  general  application  of  this  system  to  exhaust  heating  is 
shown  in  Fig.  132.  Exhaust  steam  is  brought  from  the  engine  as 
shown;  one  branch  is  connected  with  a  feed-water  heater,  while  the 
other  is  carried  upward  and  through  a  grease  extractor,  where  it 
branches  again,  one  line  leading  outboard  through  a  back-pressure 
valve  and  the  other  connecting  with  the  heating  main.  A  live  steam 
connection  is  made  through  a  reducing  valve,  as  in  the  ordinary 
system.  Valved  connections  are  made  with  the  coils  and  radiators 
in  the  usual  manner;  but  the  return  valves  are  replaced  by  the  special 
thermostatic  valves  described  above. 

The  main  return  is  brought  down  to  a  vacuum  pump  which  dis- 
charges into  a  return  tank,  where  the  air  is  separated  from  the  water 
and  passes  off  through  the  vapor  pipe  at  the  top.  The  condensation 
then  flows  into  the  feed-water  heater,  from  which  it  is  automatically 
pumped  back  into  the  boilers.  The  cold-water  feed  supply  is  con- 
nected with  the  return  tank,  and  a  small  cold.- water  jet  is  connected 
into  the  suction  at  the  vacuum  pump  for  increasing  the  vacuum  in  the 
heating  system  by  the  condensation  of  steam  at  this  point. 

Paul  System.  In  this  system  the  suction  is  connected  with  the 
air-valves  instead  of  the  returns,  and  the  vacuum  is  produced  by 
means  of  a  steam  ejector  instead  of  a  pump.  The  returns  are  carried 
back  to  a  receiving  tank,  and  pumped  back  to  the  boiler  in  the  usual 
manner.  The  ejector  in  this  case  is  called  the  exhauster. 

Fig.  133  shows  the  general  method  of  making  the  pipe  connections 
with  the  radiators  in  this  system;  and  Fig.  134,  the  details  of  connec- 
tion at  the  exhauster. 

A  A  are  the  returns  from  the  air-valves,  and  connect  with  the 
exhausters  as  shown.  Live  steam  is  admitted  in  small  quantities 
through  the  valves  B  B ;  and  the  mixture  of  air  and  steam  is  discharged 
outboard  through  the  pipe  C.  D  D  are  gauges  showing  the  pressure 
in  the  system;  and  E  E  are  check-valves.  The  advantage  of  this 
system  depends  principally  upon  the  quick  removal  of  air  from  the 
various  radiators  and  pipes,  which  constitutes  the  principal  obstruction 


146 


HEATING  AND  VENTILATION 


to  circulation ;  the  inductive  action  in  many  cases  is  sufficient  to  cause 
the  system  to  operate  somewhat  below  atmospheric  pressure. 

Where  exhaust  steam  is  used  for  heating,  the  radiators  should 


PAUL    SYSTEM  Of  HEATIN6 


Fig.  133.    Shoeing  General  Method  of  Making  Pipe  and  Radiator  Connections  in 

Paul  System. 


be  somewhat  increased  in  size,  owing  to  the  lower  temperature  of 
the  steam.  It  is  common  practice  to  add  from  20  to  30  per  cent  to 
the  sizes  required  for  low-pressure  live  steam. 


HEATING  AND  VENTILATION 


147 


FORCED  BLAST 

In  a  system  of  forced  circulation  by  means  of  a  fan  or  blower 
the  action  is  positive  and  practically  constant  under  all  usual  con- 
ditions of  outside  temperature  and  wind  action..     This  gives  it  a 
decided  advantage  o>ver  natural  or  gravity  methods,  which  are  af- 
A  A 


Fig.  134.    Details  of  Connections  at  Exhauster,  Paul  System. 

fected  to  a  greater  or  less  degree  by  changes  in  wind-pressure,  and 
makes  it  especially  adapted  to  the  ventilation  and  warming  of  large 
buildings  such  as  shops,  factories,  schools,  churches,  halls,  theaters, 
etc.,  where  large  and  definite  air-quantities  are  required. 

Exhaust   Method.    This  consists  in  drawing  the  air  out  of  a 
building,  and  providing  for  the  heat  thus  carried  away  by  placing 


148  HEATING  AND  VENTILATION 

steam  coils  under  windows  or  in  other  positions  where  the  inward 
leakage  is  supposed  to  be  the  greatest.  When  this  method  is  used,  a 
partial  vacuum  is  created  within  the  building  or  room,  and  all  currents 
and  leaks  are  inward ;  there  is  nothing  to  govern  definitely  the  quality 
and  place  of  introduction  of  the  air,  and  it  is  difficult  to  provide  suit- 
able means  for  warming  it. 

Plenum  Method.  In  this  case^the  air  is  forced  into  the  building, 
and  its  quality,  temperature,  and  point  of  admission  are  completely 
under  control.  All  spaces  are  filled  with  air  under  a  slight  pressure, 
and  the  leakage  is  outward,  thus  preventing  the  drawing  of  foul  air 
into  the  room  from  any  outside  source.  But  above  all,  ample  oppor- 
tunity is  given  for  properly  warming  the  air  by  means  of  heaters, 
either  in  direct  connection  with  the  fan  or  in  separate  passages  leading 
to  the  various  rooms.- 

Form  of  Heating  Surface.  The  best«type  of  heater  for  any 
particular  case  will  depend  upon  the  volume  and  final  temperature 
of  the  air,  the  steam  pressure,  and  the  available  space.  When  the 
air  is  to  be  heated  to  a  high  temperature  for  both  warming  and  venti- 
lating a  building,  as  in  the  case  of  a  shop  or  mill,  heaters  of  the  general 
form  shown  in  Figs.  135,  136,  and  137  are  used.  These  may  also  be 
adapted  to  all  classes  of  work  by  varying  the  proportions  as  required. 
They  can  be  made  shallow  and  of  large  superficial  area,  for  the  com- 
paratively low  temperatures  used  in  purely  ventilating  work;  or 
deeper,  with  less  height  and  breadth,  as  higher  temperatures  are 
required. 

Fig,  135  shows  in  section  a  heater  of  this  type,  and  illustrates 
the  circulation  of  steam  through  it.  It  consists  of  sectional  cast-iron 
bases  with  loops  of  wrought-iron  pipe_  connected  as  shown.  The 
steam  enters  the  upper  part  of  the  bases  or  headers,  and  passes  up 
one  side  of  the  loops,  then  across  the  top  and  down  on  the  other  side, 
where  the  condensation  is  taken  off  through"  the  return  drip,  which 
is  separated  from  the  inlet  by  a  partition.  These  heaters  are  made 
up  in  sections  of  2  and  4  rows  of  pipes  each.  The  height  varies  from 
3^  to  9  feet,  and. the  width. from  3  feet  to  7  feet  in  the  standard  sizes. 
They  are  usually  made  up  of  1-inch  pipe,  although  IJ-inch  is  commonly 
used  in  the  larger  sizes.  Fig.  136  shows  another  form;  in  this  case 
all  the  loops  are  made  of  practically  the  same  length  by  the  special 
form  of  construction  shown.  This  is  claimed  to  prevent  the  short- 


HEATING  AND  VENTILATION 


149 


circuiting  of  steam  through  the  shorter  loops,  which  causes  the  outer 
pipes  to  remain  cold.     This  form  of  heater  is  usually  encased  in  a 


Fig.  135.    Showing  Circulation  of  Steam  in  Large  Coil-Pipe  Radiator  for 
Heating  Mills,  Shops,  etc. 

sheet-steel  housing  as  shown  in  Fig.  137,  but  may  be  supported  on  3 
foundation  between  brick  walls  if  desired. 


150 


HEATING  AND  VENTILATION 


Fig.  138  shows  a  special  form  of  heater  particularly  adapted  to 
ventilating  work  where  the  air  does  not  have  to  be  raised  above  70  or 
80  degrees.  It  is  made  up  of  1-inch  wrought-iron  pipe  connected 


with  supply  and  return  headers;  each  section  contains  14  pipes,  and 
they  are  usually  made  up  in  groups  of  5  sections  each.  These  coils 
are  supported  upon  tee-irons  resting  upon  a  brick  foundation.  Heat- 


HEATING  AND  VENTILATION 


151 


ers  of  this  form  are  usually  made  to  extend  across  the  side  of  a  room 
with  brick  walls  at  the  sides,  instead  of  being  encased  in  steel  housings. 

Fig.  139  shows  a  front  view  of  a  cast-iron  sectional  heater  for 
use  under  the  same  conditions  as  the  pipe  heaters  already  described. 
This  heater  is  macteoip  of  several  banks  of  sections,  like  the  one  shown 
in  the  cut,  and  enclosed  in  a  steel-plate  casing. 

Cast-iron  indirect  radiators  of  the  pin  type  are  well  adapted  for 
use  in  connection  with  mechanical  ventilation,  and  also  for  heating 


Fig.  137.    Large  Coil-Pipe  Radiator  Encased  in  Sheet-Steel  Housing. 

where  the  air-volume  is  large  and  the  temperature  not  too  high,  as 
in  churches  and  halls.  They  make  a  convenient  form  of  heater  for 
schoolhouse  and  similar  work,  for,  being  shallow,  they  can  be  sup- 
ported upon  I-beams  at  such  an  elevation  that  the  condensation  will  be 
returned  to  the  boilers  by  gravity. 

In  the  case  of  vertical  pipe  heaters,  the  bases  are  below  the  water- 
line  of  the  boilers,  and  the  condensation  must  be  returned  by  the  use 
of  pumps  and  traps. 


152 


HEATING  AND  VENTILATION 


Efficiency  of  Pipe  Heaters.  The  efficiency  of  the  heaters  used  in 
connection  with  forced  blast  varies  greatly,  depending  upon  the 
temperature  of  the  entering  air,  its  velocity  between  the  pipes,  the 
temperature  to  which  it  is  raised,  and  the  steam  pressure  carried  in 
the  heater.  The  general  method  in  which  the  heater  is  made  up  is 
also  an  important  factor. 

In  designing  a  heater  of  this  kind,  care  must  be  taken  that  the 
free  area  between  the  pipes  is  not  contracted  to  such  an  extent  that 
an  excessive  velocity  will  be  required  to  pass  the  given  quantity  of 

CE/L/NG  UNE 


A/R  VALVE 
PLAN  AT  SUPPLY  END 


FRONT  V/EW 


S/0£      V/EW 


Fig.  138.    Heater  Especially  Adapted  to  Ventilation  where  Air  does  not  Have  to  be  Heated 

above  70  to  80  degrees  F. 

air  through  it.  In  ordinary  work  it  is  customary  to  assume  a  velocity 
of  800  to  1,000  feet  per  minute;  higher  velocities  call  for  a  greater 
pressure  on  the  fan,  which  is  not  desirable  in  ventilating  work. 

In  the  heaters  shown,  about  .4  of  the  total  area  is  free  for  the 
passage  of  air;  that  is,  a  heater  5  feet  wide  and  6  feet  high  would 
have  a  total  area  of  5  X  6  =  30  square  feet,  and  a  free  area  between 
the  pipes  of  30  X  .4  =  12  square  feet.  The  depth  or  number  of  rows 
of  pipe  does  not  affect  the  free  area,  although  the  friction  is  increased 
and  additional  work  is  thrown  upon  the  fan.  The  efficiency  in  any 


HEATING  AND  VENTILATION 


153 


given  heater  will  be  increased  by  increasing  the  velocity  of  the  air 
through  it;  but  the  final  temperature  will  be  diminished;  that  is, 
a  larger  quantity  of  air  will  be  heated  to  a  lower  temperature  in  the 
second  case,  and,  while  the  total  heat  given  off  is  greater,  the  air- 
quantity  increases  more  rapidly  than  the  heat-quantity,  which  causes 
a  drop  in  temperature. 

Increasing  the  number  of  rows  of  pipe  in  a  heater,  with  a  con- 
stant air-quantity,  increases  the  final  temperature  of  the  air,  but 
diminishes  the  efficiency  of  the  heater,  because  the  average  difference 
in  temperature  between  the  air  and  the  steam  is  less.  Increasing 
the  steam  pressure  in  the 
heater  (and  consequently  its 
temperature)  increases  both 
the  final  temperature  of  the 
air  and  the  efficiency  of  the 
heater.  Table  XXX  has  been 
prepared  from  different  tests, 
and  may  be  used  as  a  guide 
in  computing  probable  results 
under  ordinary  working  con- 
ditions. In  this  table  it  is 
assumed  that  the  air  enters 
the  heater  at  a  temperature  of 
zero  and  passes  between  the 
pipes  with  a  velocity  of  800 
feet  per  minute.  Column  1 
gives  the  number  of  rows  of 
pipe  in  the  heater,  ranging 
from  4  to  20  rows;  and  columns  2,  3,  and  4,  show  the  final  tempera- 
ture to  which  the  entering  air  will  be  raised  from  zero  under  various 
pressures.  Under  5  pounds  pressure,  for  example,  the  rise  in  tem- 
perature ranges  from  30  to  140  degrees;  under  20  pounds,  35  to  150 
degrees;  and  under  60  pounds,  45  to  170  degrees.  Columns  5, 6,  and 
7  give  approximately  the  corresponding  efficiency  of  the  heater.  For 
example,  air  passing  through  a  heater  10  pipes  deep  and  carrying  20 
pounds  pressure,  will  be  raised  to  a  temperature  of  90  degrees,  and 
the  heater  will  have  an  efficiency  of  1,650  B.  T.  U.  per  square  foot  of 
surface  per  hour. 


Fig.  139.    Front  View  of  Cast-Iron  Sectional 
Heater.    The  Banks  of  Sections  are  En- 
closed in  a  Steel- Plate  Casing. 


154 


HEATING  AND  VENTILATION 


TABLE  XXX 
Data  Concerning  Pipe  Heaters 

Temperature  of  entering  air,  zero. — Velocity  of  air  between  the  pipes, 
800  feet  per  minute. 


TEMPERATURE  TO  WHICH  AIR  WILL 
BE  RAISED  FROM  ZERO 

EFFICIENCY  OF  HEATING  SURFACE  iNB.T.U., 
PER  SQUARE  FOOT  PER  HOUR 

Rows  OF 

PIPE  DEEP 

Steam  Pressure  in  Heater 

Steam  Pressure  in  Heater 

5  Ibs. 

20  Ibs. 

60  Ibs. 

5  Ibs. 

20  Ibs. 

60  Ibs. 

4 

30 

35 

45 

1,600 

,800 

2,000 

6 

50 

55 

65 

1,600 

,800 

2,000 

8 

65 

70 

85 

1,500 

,650 

1,850 

10 

80 

90 

105 

,500 

,650 

1,850 

12 

95 

105 

125 

,500 

,650 

1,850 

14 

105 

120 

140 

,400 

,500 

1,700 

16 

120 

130 

150 

,400 

,500 

1,700 

18 

130 

140 

160 

,300 

,400 

1,600 

20 

140 

150 

170 

,300 

,400 

1,600 

For  a  velocity  of  1,000  feet,  multiply  the  temperatures  given  in 
the  table  by  .9,  and  the  efficiencies  by  1.1. 

Example.  How  many  square  feet  of  radiation  will  be  required  to  raise 
600,000  cubic  feet  of  air  per  hour  from  zero  to  80  degrees,  with  a  velocity 
through  the  heater  of  800  feet  per  minute  and  a  steam  pressure  of  5  pounds? 
What  must  be  the  total  area  of  the  heater  front,  and  how  many  rows  of 
pipes  must  it  have? 

Referring  back  to  the  formula  for  heat  required  for  ventilation, 
we  have 


600,000  X  80 
.  55 


=  872,727  B.  T.  U.  required. 


Referring  to  Table  XXX,  we  find  that  for  the  above  conditions  a 
heater  10  pipes  deep  is  required,  and  that  an  efficiency  of  1,500 


B.  T.  U.  will   be  obtained.     Then 


872,727 
1,500 


=   582  square  feet  of 


surface  required,  which  may   be   taken  as  600  in   round  numbers. 

600,000  ,  .     ,          .     .  .  ,   10,000 

—  =  10,000  cubic  feet  of  air  per  minute;  and  =12.5 

60  oOO 

square  feet  of  free  area  required  through  the  heater.     If  we  assume 
.4  of  the  total  heater  front  to  be  free  for  the  passage  of  air,  then 

— ~  =  31  square  feet,  the  total  area  required. 


HEATING  AND  VENTILATION 


155 


For  convenience  in  estimating  the  approximate  dimensions  of 
a  heater,  Table  XXXI  is  given.  The  standard  heaters  made  by  dif- 
ferent manufacturers  vary  somewhat,  but  the  dimensions  given  in 
the  table  represent  average  practice.  Column  3  gives  the  square 
feet  of  heating  surf  ace  In  a  single  row  of  pipes  of  the  dimensions  given 
in  columns  1  and  2;  and  column  4  gives  the  free  area  between  the 
pipes. 

TABLE   XXXI 

Dimensions  of  Heaters 


WIDTH  OP  SECTION 

HEIGHT  op  PIPES 

SQUARE  FEET  OF 
SURFACE 

FREE  AREA  THROUGH 
HEATER  IN  SQ.  FT. 

3  feet 

3  feet  6  inches 

20 

4.2 

3    " 

4     "    0       " 

22 

4.8 

3    " 

4    "    6       " 

25 

5.4 

3    " 

5    "    0       " 

28 

6.0 

4    " 

4     "6       " 

34 

7.2 

4    " 

5     "    0       " 

38 

8.0 

4    " 

5     "    6       " 

42 

8.8 

4    " 

6     "    0       " 

45 

9.6 

5    " 

5     "    6       " 

52 

11.0 

5    " 

6     "    0       " 

57 

12.0 

5    " 

6     "    6       " 

62 

13.0 

5    " 

7  .  "    0       " 

67 

14.0 

6    " 

6     "    6       " 

75 

15.6 

6    " 

7     "    0       " 

81 

16.8 

6    " 

7     "    6 

87 

18.0 

6    " 

8     "    0       " 

92 

19.2 

7    " 

7     "    6       " 

98 

21.0 

7    " 

8     "    0       " 

108 

22.4 

7    " 

8     "    6       " 

109 

23.8 

7    " 

9     "    0       " 

116 

25.2 

In  calculating  the  total  height  of  the  heater,  add  1  foot  for  the 
base. 

These  sections  are  made  up  of  1-inch  pipe,  except  the  last  or 
7-foot  sections,  which  are  made  of  IJ-inch  pipe. 

Using  this  table  in  connection  with  the  example  just  given,  we 
should  look  in  the  last  column  for  a  section  having  a  free  area  of  12.5 
square  feet ;  here  we  find  that  a  5  feet  by  6  feet  6  inches  section  has  a 
free  opening  of  13  square  feet  and  a  radiating  surface  of  62  square 


156  HEATING  AND  VENTILATION 

feet.  The  conditions  call  for  10  rows  of  pipes  and  10  X  62  =  620 
square  feet  of  radiating  surface,  which  is  slightly  more  than  called  for, 
but  which  would  be  near  enough  for  all  practical  purposes. 

EXAMPLE  FOR  PRACTICE 

Compute  the  dimensions  of  a  heater  to  warm  20,000  cubic  feet 
of  air  per  minute  from  10  below  zero  to  70  degrees  above,  with  5 
pounds  steam  pressure. 

ANS.    1,164  sq.  ft.  of  rad.  surface  10  pipes  deep. 
25  sq.  ft.  free  area  through  heater. 

Use  twenty  5  ft.  by  6  ft.  sections,  side  by  side,  which  gives  24 
square  feet  area  and  1,140  square  feet  of  surface. 

The  general  method  of  computing  the  size  of  heater  for  any  given 
building  is  the  same  as  in  the  case  of  indirect  heating.  First  obtain 
the  B.  T.  U.  required  for  ventilation,  and  to  that  add  the  heat  loss 
through  walls,  etc.;  and  divide  the  result  by  the  efficiency  of  the 
heater  under  the  given  conditions. 

Example.  An  audience  hall  is  to  be  provided  with  400,000  cubic  feet 
of  air  per  hour.  The  heat  loss  through  walls,  etc.,  is  250,000  B.T.U.  per 
hour  in  zero  weather.  What  will  be  the  size  of  heater,  and  how  many  rows 
of  pipe  deep  must  it  be,  with  20  pounds  steam  pressure? 

400,000X70  =  509j()90 B  T  n  for ventiiation. 

oo 

Therefore  250,000  +  509,090  =  759,090  B.  T.  U.,  total  to  be  supplied. 
We  must  next  find  to  what  temperature  the  entering  air  must 
be  raised  in  order  to  bring  in  the  required  amount  of  heat,  so  that  the 
number  of  rows  of  pipe  in  the  heater  may  be  obtained  and  its  corre- 
sponding efficiency  determined.  We  have  entering  the  room  for  pur- 
poses of  ventilation,  400,000  cubic  feet  of  air  every  hour,  at  a  tempera- 
ture of  70  degrees;  and  the  problem  now  becomes:  To  what  tem- 
perature must  this  air  be  raised  to  carry  in  250,000  B.  T.  U.  additional 
for  warming? 

We  have -learned  that  1  B.  T.  U.  will  raise  55  cubic  feet  of  air 
1  degree.  Then  250,000  B.  T.  U.  will  raise  250,000  X  55  cubic 
feet  of  air  1  degree. 

250,000  X  55 

400,000 
The  air  in  this  case  must  be  raised  to  70  -+•  34  =  104  degrees,  to  provide 


HEATING  AND  VENTILATION  157 

for  both  ventilation  and  warming.  Referring  to  Table  XXX,  we  find 
that  a  heater  12  pipes  deep  will  be  required,  and  that  the  corre- 
sponding efficiency  of  the  heater  will  be  1,650  B.  T.  IT.  Then  — '— 

1  ,ooO 

=  460  square  feet  of  surface  required. 

Efficiency  of  Cast=Iron  Heaters.  Heaters  made  up  of  indirect 
pin  radiators  of  the  usual  depth,  have  an  efficiency  of  at  least  1,500 
B.  T.  U.,  with  steam  at  10  pounds  pressure,  and  are  easily  capable  of 
warming  air  from  zero  to  80  degrees  or  over  when  computed  on  this 
basis.  The  free  space  between  the  sections  bears  such  a  relation  to 
the  heating  surface  that  ample  area  is  provided  for  the  flow  of  air 
through  the  heater,  without  producing  an  excessive  velocity. 

The  heater  shown  in  Fig.  139  may  be  counted  on  for  an  effi- 
ciency at  least  equal  to  that  of  a  pipe  heater;  and  in  computing  the 
depth,  one  row  of  sections  may  be  taken  as  representing  4  rows  of 

Pipe- 
Pipe  Connections.     In  the  heater  shown  in  Fig.   135,  all  the 
sections  take  their  supply  from  a  common  header,  the  supply  pipe 
connecting  with  the  top,  and  the  return  being  taken  from  the  lower 
division  at  the  end,  as  shown. 

In  Fig.  137  the  base  is  divided  into  two  parts,  one  for  live  steam, 
and  the  other  for  exhaust.  The  supply  pipes  connect  with  the  upper 
compartments,  and  the  drips  are  taken  off  as  shown.  Separate  traps 
should  be  provided  for  the  two  pressures. 

The  connections  in  Fig.  136  are  similar  to  those  just  described, 
except  that  the  supply  and  return  headers,  or  bases,  are  drained 
through  separate  pipes  and  traps,  there  being  a  slight  difference  in 
pressure  between  the  two,  which  is  likely  to  interfere  with  the  proper 
drainage  if  brought  into  the  same  one.  This  heater  is  arranged  to 
take  exhaust  steam,  but  has  a  connection  for  feeding  in  live  steam 
through  a  reducing  valve  if  desired,  the  whole  heater  being  under  one 
pressure. 

In  heating  and  ventilating  work  where  a  close  regulation  of 
temperature  is  required,  it  is  usual  to  divide  the  heater  into  several 
sections, depending  upon  its  size,  and  to  provide  each  with  a  valve  in  the 
supply  and  return.  In  making  the  divisions,  special  care  should  be 
taken  to  arrange  for  as  many  combinations  as  possible.  For  example, 
a  heater  10  pipes  deep  may  be  made  up  of  three  sections — one  of 


158 


HEATING  AND  VENTILATION 


2  rows,  and  two  of  4  rows  each.  By  means  of  this  division,  2,  4,  6,  8, 
or  10  rows  of  pipe  can  be  used  at  one  time,  as  the  outside  weather 
conditions  may  require. 

When  possible,  the  return  from  each  section  should  be  provided 
with  a  water-seal  two  or  three  feet  m  depth.  In  the  case  of  overhead 
heaters,  the  returns  may  be  sealed  by  the  water-line  of  the  boiler  or 
by  the  use  of  a  special  water-line  trap;  but  vertical  pipe  heaters 
resting  on  foundations  near  the  floor  are  usually  provided  with  siphon 
loops  extending  into  a  pit.  If  this  arrangement  is  not  convenient,  a 
separate  trap  should  be  placed  on  the  return  from  each  section. 
The  main  return,  in  addition  to  its  connection  with  the  boiler  or 


LIVE    STEAM 


TRAP  TRAP 

Fig.  140.    Heater  Made  Up  of  Interchangeable  Sections. 

pump  receiver,  should  have  a  connection  with  the  sewer  for  blowing 
out  when  steam  is  first  turned  on.  Sometimes  each  section  is  pro- 
vided with  a  connection  of  this  kind. 

Large  automatic  air-valves  should  be  connected  with  each 
section;  and  it  is  well  to  supplement  these  with  a  hand  pet-cock, 
unless  individual  blow-off  valves  are  provided  as  described  above. 

If  the  fan  is  driven  by  a  steam  engine,  provision  should  be  made 
for  using  the  exhaust  in  the  heater;  and  part  of  the  sections  should 
be  so  salved  that  they  may  be  supplied  with  either  exhaust  or  live 
steam. 


HEATING  AND  VENTILATION 


159 


Fig.  140  shows  an  arrangement  in  which  all  of  the  sections  are 
interchangeable. 

From  50  to  60  square  feet  of  radiating  surface  should  be  provided 
in  the  exhaust  portion  of  the  heater  for  each  engine  horse-power, 
and  should  be  divided^into  at  least  three  sections,  so  that  it  can  be 
proportioned  to  the  requirements  of  different  outside  temperatures. 

Pipe  Sizes.  The  sizes  of  the  mains  and  branches  may  be  com- 
puted from  the  tables  already  given  in  Part  II,  taking  into  account 
the  higher  efficiency  of  the  heater  and  the  short  runs  of  piping. 

Table  XXXII,  based  on  experience,  has  been  found  to  give 
satisfactory  results  when  the  apparatus  is  near  the  boilers.  If  the 
main  supply  pipe  is  of  considerable  length,  its  diameter  should  be 
checked  by  the  method  previously  given. 

TABLE     XXXII 
Pipe  Sizes 


SQUARE 

FEET  OF  SURFACE 

DIAMETER  OF  STEAM  PIPE 

DIAMETER  OF  RETURN 

150 

2     inches 

H  inches 

300 

2* 

• 

1* 

500 

3 

2 

700 

3i 

2 

1,000 

4 

2J 

2,000 

5 

2* 

3,000 

6 

3 

Heaters  of  the  patterns  shown  in  Figs.  135,  136,  and  137  are 
usually  tapped  at  the  factory  for  high  or  low  pressure  as  desired, 
and  these  sizes  may  be  followed  in  making  the  pipe  connections. 

The  sizes  marked  on  Fig.  136  may  be  used  for  all  ordinary  work 
where  the  pressure  runs  from  5  to  20  pounds;  for  pressures  above 
that,  the  supply  connections  may  be  reduced  one  size. 

FANS 

There  are  two  types  of  fans  in  common  use,  known  as  the  cen- 
trifugal fan  or  blower,  and  the  disc  fan  or  propeller.  The  former 
consists  of  a  number  of  straight  or  slightly  curved  blades  extending 
radially  from  an  axis,  as  shown  in  Fig.  141.  When  the  fan  is  in 
motion,  the  air  in  contact  with  the  blades  is  thrown  outward  by  the 
action  of  centrifugal  force,  and  delivered  at  the  circumference  or 


160 


HEATING  AND  VENTILATION 


periphery  of  the  wheel.     A  partial  vacuum  is  thus  produced  at  the 

center  of  the  wheel,  and  air  from  the  outside  flows  in  to  take  the 

place  of  that  which  has  been  discharged. 

Fig.  142  illustrates  the  action  of  a  centrifugal  fan,  the  arrows 

showing  the  path  of  the  air. 

This  type  of  fan  is  usually 

enclosed    in    a   steel -plate 

casing  of  such  form  as  to 

provide  for  the  free  move- 
ment of  the  air  as  it  es- 
capes from  the  periphery 

of  the  wheel.     An  opening 

in  the  circumference  of  the 

casing   serves    as  an  outlet 

into  the  distributing  ducts 

which  carry  the  air  to  the 

various  rooms  to  be  venti- 
lated. 

A  fan  with  casing,   is 

shown  in  Fig.   143;  and  a 

combined  heater  and  fan, 

with  direct -connected  engine,  is  shown  in  Fig.  144. 

The  discharge  opening  can  be  located  in  any  position  desired, 

either  up,  down,  top  horizontal,  bottom  horizontal,  or  at  any  angle. 

Where  the  height  of  the  fan  room  is 
limited,  a  form  called  the  three-quarter 
housing  may  be  used,  in  which  the  lower 
part  of  the  casing  is  replaced  by  a  brick 
or  cemented  pit  extending  below  the  floor- 
level  as  shown  in  Fig.  145. 

Another  form  of  centrifugal  fan  is 
shown  in  Fig.  146.  This  is  known  as  the 
cone  fan,  and  is  commonly  placed  in  an 
opening  in  a  brick  wall,  and  discharges  air 
from  its  entire  periphery  into  a  room  called 
a  plenum  chamber,  with  which  the  various 

distributing  ducts  connect. 

This  fan  is  often   made   double  by  placing  two  wheels  back  to 


Fig.  141.    Centrifugal  Fan  or  Blower. 


Fig.  142.  Illustrating  Action 
of  Centrifugal  Fan.  The 
Arrows  Show  the  Path  of 
the  Air. 


HEATING  AND  VENTILATION 


16) 


back  and  surrounding  them  with  a  steel  casing  in  a  similar  manner 
to  the  one  shown  in  Fig.  143. 

Cone  fans  are  particularly  adapted  to  church  and  schoolhouse 
work,  as  they  are  capable  of  moving  large  volumes  of  air  at  moderate 
speeds. 

Fig.  147  shows  a  form  of  small  direct-connected  exhauster  com- 
monly used  for  ventilating  toilet-rooms,  chemical  hoods,  etc. 

Centrifugal  fans  are  used  almost  exclusively  for  supplying  air 
for  the  ventilation  of  buildings,  and  for  forced-blast  heating.  They 
are  also  used  as  exhausters 
for  removing  the  air  from 
buildings  in  cases  where 
there  is  considerable  resist- 
ance due  to  the  small  size 
or  excessive  length  of  the 
discharge  ducts. 

General  Proportions. 
The  general  form  of  a  fan 
wheel  is  shown  in  Fig.  141, 
which  represents  a  single 
spider  wheel  with  curved 
blades.  Those  over  4  feet 
in  diameter  usually  have 
two  spiders,  while  fans  of 
large  size  are  often  pro- 
vided with  three  or  more. 
The  number  of  floats  or 
blades  commonly  varies 
from  six  to  twelve,  depending  upon  the  diameter  of  the  fan.  They 
are  made  both  curved  and  straight;  the  former,  it  is  claimed,  run 
more  quietly,  but,  if  curved  too  much,  will  not  work  so  well  against 
a  high  pressure  as  the  latter  form. 

The  relative  proportions  of  a  fan  wheel  vary  somewhat  in  the 
case  of  different  makes.  The  following  are  averages  taken  from  fans 
of  different  sizes  as  made  by  several  well-known  manufacturers  for 
general  ventilating  and  similar  work: 

Width  of  fan  at  center  =  Diameter  X  .52 

Width  of  fan  at  perimeter  =  Width  at  center  X  .8 

Diameter  of  inlet  =  Diameter  of  wheel  X  .68 


Fig.  143.    Centrifugal  Fan  with  Casing. 


162 


HEATING  AND  VENTILATION 


Fig.  144.    Combined  Heater  and  Centrifugal  Fan  with  Direct-Connected  Engine. 


Fig.  145.    Centrifugal  Fan  in  "Three-Quarter  Housing."    Used  where  Headroom  is 
Limited ;  Extra  Space  Provided  by  Pit  under  Floor-Level. 


HEATING  AND  VENTILATION 


163 


Fans  are  made  both  with  double  and  with  single  inlets,  the 
former  being  called  blowers  and  the  latter  exhausters.  The  size  of 
a  fan  is  commonly  expressed  in  inches,  which  means  the  approximate 
height  of  the  casing  of  a  full-housed  fan.  The  diameter  of  the  wheel 
is  usually  expressed^in  feet,  and  can  be  found  in  any  given  case  by 
dividing  the  size  in  inches  by  20.  For  example,  a  120-inch  fan  has  a 
wheel  120  -r  20  =  6  feet  in  diameter. 


Fig.  146.     "Cone"  Fan. 


Discharges  through  Opening  in  Wall  into  a  " 
Connecting  with  Distributing  Ducts. 


Plenum  Chamber' 


Theory  of  Centrifugal  Fans.  The  action  of  a  fan  is  aft'ected 
to  such  an  extent  by  the  various  conditions  under  which  it  operates, 
that  it  is  impossible  to  give  fixed  rules  for  determining  the  exact 
results  to  be  expected  in  any  particular  instance.  This  being  the 
case,  it  seems  best  to  take  up  the  matter  briefly  from  a  theoretical 


164 


HEATING  AND  VENTILATION 


standpoint,  and  then  show  what  corrections  are  necessary  in  the 
case  of  a  given  fan  under  actual  working  conditions. 

There  are  various  methods  for  determining  the  capacity  of  a 
fan  at  different  speeds,  and  the  power  necessary  to  drive  it;  each 
manufacturer  has  his  own  formulae  for  this  purpose,  based  upon 
tests  of  his  own  particular  fans.  The  methods  given  here  apply 
in  a  general  way  to  fans  having  proportions  which  represent  the 
average  of  several  standard  makes;  and  the  results  obtained  will  be 


Fig.  147.  Small,  Direct-Connected  Exhauster  for  Ventilating  Toilet-Rooms,  Chemical 

Hoods,  etc. 

found   to  correspond   well   with   those  obtained   in   practice   under 
ordinary  conditions. 

As  already  stated,  the  rotation  of  a  fan  of  this  type  sets  in  motion 
the  air  between  the  blades,  which,  by  the  action  of  centrifugal  force, 
is  delivered  at  the  periphery  of  the  wheel  into  the  casing  surrounding 
it.  As  the  velocity  of  flow  through  the  discharge  outlet  depends 
upon  the  pressure  or  head  within  the  casing,  and  this  in  turn  upon 
the  velocity  of  the  blades,  it  becomes  necessary  to  examine  briefly 
into  the  relations  existing  between  these  quantities. 


HEATING  AND  VENTILATION 


165 


Pressure.  The  pressure  referred  to  in  connection  with  a  fan, 
is  that  in  the  discharge  outlet,  and  represents  the  force  which  drives 
the  air  through  the  ducts  and  flues.  The  greater  the  pressure  with  a 
given  resistance  in  the  pipes,  the  greater  will  be  the  volume  of  air 
delivered;  and  the  greater  the  resistance,  the  greater  the  pressure 
required  to  deliver  a  given  quantity. 

The  pressure  within  a  fan  casing  is  caused  by  the  air  being 
thrown  from  the  tips  of  the  blades,  and  varies  with  the  velocity  of 
rotation;  that  is,  the  higher  the  speed  of  the  fan,  the  greater  will  be 
the  pressure  produced.  Where  the  dimensions  of  a  fan  and  casing 
are  properly  proportioned,  the  velocity  of  air-flow  through  the  outlet 
will  be  the  same  as  that  of  the  tips  of  the  blades,  and  the  pressure 
within  the  casing  will  be  that  corresponding  to  this  velocity. 

Table  XXXIII  gives  the  necessary  speed  for  fans  of  different 
diameters  to  produce  different  pressures,  and  also  the  velocity  of  air- 
flow due  to  these  pressures. 

TABLE  XXXIII 
Fan  Speeds,  Pressures,  and  Velocities  of  Air-Flow 


s« 
lee 

DIAMETER  OF  FAN  WHEEL,  IN  FEET 

-  -  - 

0  a  H 

.    &H   ^ 

a      r 

«<*£ 
t>  w 

03  0     . 

3 

4 

5 

6 

7 

8 

9 

10 

fc       S5 

I** 

®  z,  <y 

J     fe    QJ 

K&OQ 

WOW 

£o 

REVOLUTIONS  PER  MINUTE 

*&* 

i 

274 

206 

164 

137 

117 

103 

92 

82 

2,585 

| 

336 

252 

202 

168 

144 

126 

112 

101 

3,165 

338 

291 

232 

194 

166 

146 

129 

116 

3,653 

f 

433 

325 

260 

217 

186 

163 

144 

130 

4,084 

The  application  of  this  table  will  be  made  plain  by  a  brief  dis- 
cussion of  blast  area. 

Blast  Area.  When  the  outlet  from  a  fan  casing  is  small,  the  air 
will  pass  out  with  a  velocity  equal  to  that  of  the  tips  of  the  blades;  and 
the  pressure  within  the  casing  will  be  that  corresponding  to  the 
tip  velocity.  That  is,  a  3-foot  fan  wheel  revolving  at  a  speed  of  274 
revolutions  per  minute  will  produce  a  pressure  within  the  fan  casing 
of  J  ounce  per  square  inch,  and  will  cause  a  velocity  of  flow  through 
the  discharge  outlet  of  2,585  feet  per  minute  (see  Table  XXXIII). 


166  HEATING  AND  VENTILATION 

Now,  if  the  opening  be  slowly  increased,  while  the  speed  of  the  fan 
remains  constant,  the  air  will  continue  to  flow  with  the  same  velocity 
until  a  certain  area  of  outlet  is  reached.  If  the  outlet  be  still  further 
increased,  the  pressure  in  the  casing  will  begin  to  drop,  and  the 
velocity  of  outflow  become  less  than  the  tip  velocity.  The  effective 
area  of  outlet  at  the  point  when  this  change  begins  to  take  place,  is 
called  the  blast  area  or  capacity  area  of  the  fan.  This  varies  some- 
what with  different  types  and  makes  of  fans;  but  for  the  common 
form  of  blower,  it  is  approximately  J  of  the  projected  area  of  the  fan 

opening  at  the  periphery — that  is,  — - — ,  in  which  D  is  the  diameter 

o 

of  the  fan  wheel,  and  w  its  width  at  the  periphery.  It  has  already 
been  stated  under  "General  Proportions"  that  W  =  .52  D,  and  w  =  .8 

TT7                              ..    A      DX.8JF     DX.8X.52D         .  n, 
W\  so  that  we  may  write  A  =  -   — = =  .14  D", 

o  o 

in  which  A  —  the  blast  area,  and  D  the  diameter  of  the  fan. 

As  a  matter  of  fact,  the  outlet  of  a  fan  casing  is  always  made 
larger  than  the  blast  area;  and  the  result  is  that  the  pressure  drops 
below  that  due  to  the  tip  velocity,  and  the  velocity  of  flow  through 
the  outlet  becomes  less  than  that  given  in  the  last  column  of  Table 
XXXIII  for  any  given  speed  of  fan. 

Effective  Area  of  Outlet.  The  size  of  discharge  outlet  varies 
somewhat  for  different  makes;  but  for  a  large  number  of  fans  ex- 
amined it  was  found  to  average  about  2.22  times  the  blast  area 
as  computed  by  the  above  method.  When  air  or  a  liquid  flows 
through  an  orifice,  the  stream  is  more  or  less  contracted,  depending 
upon  the  form  of  the  orifice. 

In  the  case  of  a  fan  outlet,  the  effective  area  may  be  taken  as  about 
.8  of  the  actual  area.  This  makes  the  effective  area  of  a  fan  outlet 
equal  to  .8  X  2.22  =  1 .78  times  the  blast  area. 

Table  XXXIV  gives  the  effective  areas  of  fans  of  different 
diameter  as  computed  by  the  above  method.  That  is,  Effective 
area-  .14D2  X  1.78  =  .25Z)2. 

Speed.  We  have  seen  that  when  the  discharge  outlet  is  made 
larger  than  the  blast  area,  the  pressure  within  the  fan  casing  drops 
below  that  due  to  the  tip  velocity;  so  that,  in  order  to  bring  the  pres- 
sure up  to  its  original  point,  the  speed  of  the  fan  must  be  increased 
above  that  given  in  Table  XXXIII. 


HEATING  AND  VENTILATION  167 

TABLE  XXXIV 
Effective  Areas  of  Fans 


DIAMETER  OF  FAN,  IN  FEET 


EFFECTIVE  AREA  OF  OUTLET,  IN 
SQUARE  FEET 


3 
4 
5 
6 

7 

8 

9 

10 


2.3 

4.0 

6.3 

9.1 

12.3 

16.0 

20.4 

25.2 


Tests  upon  a  fan  of  practically  the  same  proportions  as  those 
previously  given,  show  that,  when  the  effective  outlet  area  is  made 
1 . 78  the  blast  area,  the  speed  must  be  increased  1 . 2  times  in  order 
to  keep  the  pressure  at  the  same  point  as  when  the  outlet  is  equal 
to  or  less  than  the  blast  area. 

Capacity.  The  capacity  of  a  fan  is  the  volume  of  air  discharged 
in  a  given  time,  and  is  usually  expressed  in  cubic  feet  per  minute. 
It  is  equal  to  the  effective  area  of  discharge  multiplied  by  the  velocity 
of  flow  through  it. 

Example.  At  what  speed  must  a  6-foot  fan  be  run  to  maintain  a  pres- 
sure of  \  ounce,  and  what  volume  of  air  will  be  delivered  per  minute? 

From  Table  XXXIII  we  find  that  a  6-foot  fan  must  run  at  a 
speed  of  194  revolutions  per  minute  to  maintain  the  given  pressure 
when  the  outlet  is  equal  to  the  blast  area,  or  194  X  1.2  =  233  revo- 
lutions per  minute  under  actual  conditions.  The  velocity  of  flow 
through  the  outlet  at  \  ounce  pressure,  is  3,653  feet  per  minute  (Table 
XXXIII) ;  and  the  effective  area  of  outlet  of  a  6-foot  fan  is  9 . 1  square 
feet  (Table  XXXIV).  Therefore  the  volume  of  air  delivered  per 
minute  is  equal  to  9 . 1  X  3,653  =  33,242  cubic  feet. 

Example.  It  is  desired  to  move  52,000  cubic  feet  of  air  per 
minute  at  a  pressure  of  J  ounce.  What  size  and  speed  of  fan  will 
be  required?  Looking  in  Table  XXXIII,  we  find  that  the  velocity 
through  the  fan  outlet  for  J-bunce  pressure  is  2,585,  which  calls  for 
an  outlet  area  of  52,000  •*-  2,585  =  20.1  square  feet.  Looking  in 
Table  XXXIV,  we  find  this  corresponds  very  nearly  to  a  9-foot  fan, 
which  is  the  size  called  for.  Referring  again  to  Table  XXXIII,  the 
speed  necessary  to  maintain  the  required  pressure  under  the  given 
conditions  is  found  to  be  92  X  1.2  =  110  revolutions  per  minute. 


168  HEATING  AND  VENTILATION 

Effect  of  Resistance.  Thus  far  it  has  been  assumed  that  the 
fan  was  discharging  into  the  open  air  against  atmospheric  pressure. 
The  effect  of  adding  a  resistance  by  connecting  it  with  a  series  of 
ventilating  ducts,  is  the  same  as  partially  closing  the  discharge  outlet. 
Carefully  conducted  tests  upon  this  type  of  fan  have  shown  that  the 
reduction  of  air-flow  is  very  nearly  in  proportion  to  the  reduction 
of  the  discharge  area.  That  is,  if  the  outlet  of  the  fan  is  closed  to 
one-half  its  original  area,  the  quantity  of  air  discharged  will  be  pracr 
tically  one-half  that  delivered  by  the  fan  with  a  free  opening.  The 
effect  of  attaching  a  fan  to  the  ventilating  flues  of  a  building  like  a 
schoolhouse,  church,  or  hall,  where  the  ducts  have  easy  bends  and 
where  the  velocity  of  air-flow  through  them  is  not  over  1,000  to  1,200 
feet  per  minute,  is  about  the  same  as  reducing  the  outlet  20  per  cent. 
For  factories  with  deep  heaters  and  smaller  ducts,  where  the  velocity 
runs  up  to  1,500  or  1,800  feet  per  minute,  the  effect  is  equivalent  to 
closing  the  outlet  at  least  30  per  cent,  and  even  more  in  very  large 
buildings. 

For  schoolhouses  and  similar  work  a  fan  should  not  be  run  much 
above  the  speed  necessary  to  maintain  a  pressure  of  f  ounce  at  the 
outlet.  Higher  speeds  are  accompanied  with  greater  expenditure  of 
power,  and  are  likely  to  produce  a  roaring  noise  or  to  cause  vibration. 
A  much  lower  speed  does  not  provide  sufficient  pressure  to  give  proper 
control  of  the  air-distribution  during  strong  winds.  For  factories, 
a  higher  pressure  of  f  to  f  ounce  is  more  generally  employed. 

Actually  the  pressure  is  increased  slightly  by  restricting  the  out- 
let at  constant  speed;  but  this  is  seldom  taken  into  account  in  venti- 
lating work,  as  volume,  speed,  and  power  are  the  quantities  sought. 

Example.  A  school  building  requires  32,000  cubic  feet  of  air  per  min- 
ute. What  size  and  speed  of  fan  will  be  required? 

If  the  resistance  of  the  ducts  and  flues  is  equivalent  to  cutting 
down  the  discharge  outlet  20  per  cent,  we  must  make  the  computa- 
tions for  a  fan  which  will  discharge  32,000  -s-  .8  =  40,000  cubic  feet 
in  free  air. 

Looking  in  Table  XXXIII,  we  find  the  velocity  for  f-ounce 
pressure  to  be  3,165  feet  per  minute;  therefore  the  size  of  fan  outlet 
must  be  40,000  -T-  3,165  =  12.6  square  feet,  which,  from  Table 
XXXIV,  we  find  corresponds  very  nearly  to  a  7-foot  fan. 


HEATING  AND  VENTILATION  169 

Referring  again  to  Table  XXXIII,  the  required  speed  is  found 
to  be  144  X  1.2  =  173  revolutions  per  minute. 

Example.  A  factory  requires  21,000  cubic  feet  of  air  per  minute  for 
wanning  and  ventilating.  What  size  and  speed  of  fan  will  be  required? 

21,000  -T-  .7  -  30*000,  the  volume  to  provide  for  with  a  fan 
discharging  into  free  air.  Assuming  a  pressure  of  f  ounce,  the  veloc- 
ity will  be  4,084  feet  per  minute,  from  which  the  area  of  outlet  is 
found  to  be  30,000  -r-  4,084  =  7.3  square  feet.  This,  we  find,  does 
not  correspond  to  any  of  the  sizes  given  in  Table  XXXIV.  As 
standard  fans  are  not  usually  made  in  half-sizes  above  5  feet,  we 
shall  use  a  5-foot  fan  and  run  it  at  a  higher  speed. 

A  5-foot  fan  has  an  outlet  area  of  6 . 3  square  feet,  and  at  f-ounce 
pressure  it  would  deliver  6 . 3  X  4,084  =  25,729  cubic  feet  of  air  per 
minute,  at  a  speed  of  260  X  1.2  =  312  revolutions  per  minute. 
The  volume  of  air  delivered  by  a  fan  varies  approximately  as  the 
speed ;  so,  in  order  to  bring  the  volume  up  to  the  required  30,000,  the 
speed  must  be  increased  by  the' ratio  30,000  -r-  25,729  =  =  1.16, 
making  the  final  speed  312  X  1.16  =  362  revolutions  per  minute. 
In  the  same  way,  a  6-foot  fan  could  have  been  used  and  run  at  a 
proportionally  lower  speed. 

Power  Required.  The  work  done  by  a  fan  in  moving  air  is 
represented  by  the  pressure  exerted,  multiplied  by  the  distance  through 
which  it  acts. 

Table  XXXV  gives  the  horse-power  required  for  moving  the 
air  which  will  flow  through  each  square  foot  of  the  effective  outlet 
area,  under  different  pressures. 

This  table  gives  only  the  power  necessary  for  moving  the  air, 
and  does  not  take  into  consideration  the  friction  of  the  air  in  passing 
through  the  fan,  nor  that  of  the  fan  itself. 

The  efficiency  of  a  fan  varies  with  the  speed,  the  size  of  outlet, 
and  the  pressure  against  which  the  fan  is  working.  Under  favorable 
conditions,  with  properly  proportioned  fans,  we  may  count  on  an 
efficiency  of  about  .35. 

Example.  What  horse-power  will  be  required  to  drive  an  8-foot  fan  at 
such  a  speed  as  to  maintain  a  pressure  of  £  ounce? 

An  8-foot  fan  has  an  outlet  area  of  16  square  feet  (Table  XXXIV) ; 
and  from  Table  XXXV  we  find  that  .  5  horse-power  is  required  "to 
move  the  air  which  will  flow  through  each  square  foot  of  outlet  under 


170 


HEATING  AND  VENTILATION 


TABLE  XXXV 
Power  Required  for  Moving  Air  under  Different  Pressures 


PRESSURE  IN  OUNCES  PER  SQUARE  INCH 

HORSE-POWER   FOR  MOVING  AlR  WHICH   WILL 
FLOW  THROUGH  EACH  SQUARE  FOOT  OK 
EKKECTIVE  OUTLET  AREA 

j 

.18  ' 
.33 
.50 
.70 

i-ounce  pressure.  Therefore  the  power  required  to  move  the  air 
alone  is  16  X  .5  =  8,  and  the  total  horse-power  is  8  -r-  .35  =  23. 

Effect  of  Resistance.  In  the  above  case,  it  is  assumed  that  the 
fan  is  discharging  into  free  air.  If  a  resistance  is  added,  the  effect 
is  the  same  as  partially  closing  the  outlet,  and  the  volume  of  air 
moved  and  the  horse-power  required  are  both  reduced  in  very  nearly 
the  same  proportion.  This  reduction,  as  already  stated,  may  be 
taken  as  20  per  cent  for  schoolhouse  and  similar  work,  and  30  per 
cent  for  factories. 

For  example,  if  the  fan  just  considered  was  to  be  used  for  venti- 
lating a  schoolhouse,  delivering  air  under  a  pressure  of  \  ounce,  the 
necessary  horse-power  would  be  only  23  X  .8  =  18.4.  If  used  for 
a  factory,  delivering  air  under  a  pressure  of  f  ounce,  the  required 
16  X  .7 


horse-power  would 


X  .7  =  22.3. 


General  Rules.     The  methods  above  described  may  be  briefly 
expressed  as  follows: 

CAPACITY — Q  =  A  X  v  X  F,  in  which 
Q  =  Cubic  feet  of  air  per  minute; 
A  =  Effective  area  of  fan  outlet  (Table  XXXIV) ; 
v  =  Velocity  of  flow  through  outlet; 

(3,165  (f-ounce  pressure)  for  schoolhouses,  etc.; 
(4,084  (f-ounce  pressure)  for  factories; 
F  _  j  -8  *or  schoolhouses,  etc.; 

f  .7  for  factories. 

SPEED — Take  the  speed  from  Table   XXXIII,  corresponding  to  the  given 
pressure  and  size  of  fan,  and  multiply  by  1.2. 
A  X  p  X  F 


HORSE-POWER — H.P.  = 


.35 


in  which 


H.P.  =  Horse-power; 

A  =  Effective  area  of  fan  outlet; 

p  =  Horse-power  to  move  air  which  will  flow  through  1  square  foot  of  fan 
outlet  under  given  pressure  (Table  XXXV) ; 


HEATING  AND  VENTILATION  171 


.33  for  schoolhouses,  etc.; 
.7  for  factories. 
_  j  .8  for  schoolhouses,  etc.; 
-7  for  factories. 


_  j 

j 


EXAMPLES 


1.  A  schoolhouse  requires  an  air-supply  of  30,000  cubic  feet 
per  minute.  s  What  will  be  the  required  size  of  fan,  its  speed,  and 
the  H.  P.  of  engine  to  drive  it?  f  7  ft.  in  diameter. 

ANS.  4  173  r.  p.  m. 
lOH.P. 

2.  What  will  be  the  size  and  speed  of  fan,  and  horse-power  of 
engine,  to  heat  and  ventilate  a  factory  requiring  1,080,000  cubic  feet 
of  air  per  hour?  f  6  ft.  in  diameter. 

ANS.  \  260  r.  p.  m. 

U.8  H.P. 

General  Relations.  The  following  general  relations  between  the 
volume,  pressure,  and  power  will  often  be  found  useful  in  deciding 
upon  the  size  of  a  fan  : 

(1)  The  volume  of  air  delivered  varies  directly  as  the  speed  of  the  fan; 
that  is,  doubling  the  number  of  revolutions  doubles  the  volume  of  air  de- 
livered. 

(2)  The  pressure  varies  as"  the  square  of  the  speed.     For  example,  if 
the  speed  is  doubled,  the  pressure  is  increased  2X2  =  4  times;  etc. 

(3)  The  power  required  to  run  the  fan  varies  as  the  cube  of  the  speed. 
Thus,  if  the  speed  is  doubled,  the  power  required  is  increased  2X2X2  =  8 
times;  etc. 

The  value  of  a  knowledge  of  these  relations  may  be  illustrated 
by  the  following  example: 

Suppose  for  any  reason  it  were  desired  to  double  the  volume  of 
air  delivered  by  a  certain  fan.  At  first  thought  we  might  decide  to 
use  the  same  fan  and  run  it  twice  as  fast;  but  when  we  come  to  con- 
sider the  power  required,  we  should  find  that  this  would  have  to  be 
increased  8  times,  and  it  would  probably  be  much  cheaper  in  the 
long  run  to  put  in  a  larger  fan  and  run  it  at  lower  speed. 

Disc  or  Propeller  Fans.  When  air  is  to  be  moved  against  a  very 
slight  resistance,  as  in  the  case  of  exhaust  ventilation,  the  disc  or  pro- 
peller type  of  wheel  may  be  used.  This  is  shown  in  different  forms 
in  Figs.  149  and  150.  This  type  of  fan  is  light  in  construction,  re- 
quires but  little  power  at  low  speeds,  and  is  easily  erected.  It  may  be 


172 


HEATING  AND  VENTILATION 


conveniently  placed  in  the  attic  or  upper  story  of  a  building,  where 
it  may  be  driven  either  by  a  direct-  or  belt-connected  electric  motor. 
Fig.  148  shows  a  fan  equipped  with  a  direct-connected  motor,  and 
Fig.  151  the  general  arrangement  when  a  belted  motor  is  used.  These 
fans  are  largely  used  for  the  ventilation  of  toilet  and  smoking  rooms, 
restaurants,  etc.,  and  are  usually  mounted  in  a  wall  opening,  as  shown 
in  Fig.  151.  A  damper  should  always  be  provided  for  shutting  off 
the  opening  when  the  fan  is  not  in  use.  The  fans  shown  in  Figs.  149 
and  150  are  provided  with  pulleys  for  belt  connection. 


Fig.  148.    Propeller  Fan  Direct-Connected  to  Motor. 

Fans  of  this  kind  are  often  connected  with  the  main  vent  flues 
of  large  buildings,  such  as  schools,  halls,  churches,  theaters,  etc., 
and  are  especially  adapted  for  use  in  connection  with  gravity  heating 
systems.  They  are  usually  run  by  electric  motors,  and  as  a  rule  are 
placed  in  positions  where  an  engine  could  not  be  connected,  and  also 
in  buildings  where  steam  pressure  is  not  available. 

Capacity  of  Disc  Fans.  The  capacity  of  a  disc  fan  varies  greatly 
with  the  type  and  the  conditions  under  which  it  operates.  The  rated 


HEATING  AND  VENTILATION 


173 


capacities  usually  given  in  catalogues  are  for  fans  revolving  in  free 
air — that  is,  mounted  in  an  opening  without  being  connected  with 
ducts  or  subjected  to  other  frictional  resistance. 

As  the  capacity  and  necessary  power  are  so  dependent  upon  the 
resistance  to  be  ove'pcome,  it  is  difficult  to  give  definite  rules  for 
determining  them.  The  following  data,  based  upon  actual  tests, 


Fig.  149.    Another  Form  of  Propeller  Fan,  with  Special  Type  of  Blade. 

apply  to  fans  working  against  a  resistance  such  as  would  be 
produced  by  connecting  writh  a  system  of  ducts  of  medium  length 
through  which  the  air  was  drawn  at  a  velocity  not  greater  than  600 
or  800  feet  per  minute.  Under  these  conditions,  a  good  type  of  fan 
will  propel  the  air  in  a  direction  parallel  to  the  shaft  a  distance  equal  to 
about  .7  of  its  diameter  at  each  revolution;  and  from  this  we  have 
the  equation: 


174 


HEATING  AND  VENTILATION 


Q  =  .7  D  X  K  X  A, 

in  which 

Q  =  Cubic  feet  of  air  discharged  per  minute; 
D  =  Diameter  of  fan,  in  feet; 
R  =  Revolutions  per  minute ; 
A  =  Area  of  fan,  in  square  feet. 

In  order  to  obtain  the 
best  results,  the  linear  velocity 
of  air-flow  through  the  fan 
should  range  from  800  to  1,200 
feet  per  minute. 

Table  XXXVI  gives  the 
revolutions  per  minute  for 
fans  of  different  diameter  to 
produce  a  linear  velocity  of 
1,000  feet,  the  volume  deliv- 
ered at  this  speed,  and  the 
horse-power  required . 

The  horse-power  is  com- 
puted by  allowing  .14  H.  P. 
for  each  1,000  cubic  feet  of 
air  moved,  when  the  velocity 
through  the  fan  is  800  feet 
per  minute;  .16  H.  P.  for 
1,000  feet  velocity;  and  .18  H.  P.  for  1,200  feet  velocity.  These 
factors  are  empirical,  and  based  on  tests. 


Fig.  150. 


Propeller  Fan  with  Wheel  on  Shaft 
for  Belt  Connection. 


Fig.  151.    Fan  Belt-Connected  to  Motor. 

Example.  Assuming  a  velocity  of  800  feet  per  minute  through  a  4-foot 
fan,  what  volume  will  be  delivered  per  minute,  and  what  speed  and  horse- 
power will  be  required  ? 


HEATING  AND  VENTILATION 


175 


TABLE  XXXVI 
Disc  Fans,  their  Capacity,  Speed,  etc. 


DIA.  OF  FAN,  IN 
INCHES 

REV.   PER  MIN. 

CUBIC  FEET  OP    AIR 
MOVED 

HORSE-POWER 
REQUIRED 

18 

*  952 

1,700 

.27 

24 

716 

3,100 

.50 

30 

572 

4,900 

.78 

36 

476 

7,100 

1.2 

42 

408 

9,400 

1.5 

48 

343 

12,000 

1.9 

54 

317 

15,800 

2.5 

60 

286 

19,400 

3.1 

72 

238 

28,300 

4.5 

The  area  of  a  4-foot  fan  is  12.5  square  feet;  and  at  800  velocity 
the  volume  would  be  12.5  X  800  ==  10,000  cubic  feet.  Next  solve 
for  the  speed  by  the  equation  Q  =  .7D  X  R  X  A,  which,  when 
transposed,  takes  the  form 


R  = 


Q 


.7  DX  A 

Substituting  the  known  quantities,  we  have : 

10,000 


R  = 


=  286. 


.7  X  4X  12.5 

The  horse-power  is  10  X  .14  -  1 .4. 

Fan  Engines.  A  simple,  quiet-running  engine  is  desirable 
for  use  in  connection  with  a  fan  or  blower.  The  engine  may  be  either 
horizontal  or  vertical;  and  for  schoolhouse  and  similar  work,  should 
be  provided  with  a  large  cylinder,  so  that  the  required  power  may 
be  developed  without  carrying  a  boiler  pressure  much  above  30 
pounds.  In  some  cases,  cylinders  of  such  size  are  used  that  a  boiler 
pressure  of  12  or  15  pounds  is  sufficient.  The  quantity  of  steam 
which  an  engine  consumes  is  of  minor  importance,  as  the  exhaust  can 
be  turned  into  the  coils  and  used  for  heating  purposes.  If  space 
allows,  the  engine  should  always  be  belted  to  the  fan.  Where  ft  is 
direct-connected,  as  in  Fig.  144,  there  is  likely  to  be  trouble  from 
noise,  as  any  slight  looseness  or  pounding  in  the  engine  will  be  com- 
municated to  the  air-ducts,  an'd  the  sound  will  be  carried  to  the  rooms 


176 


HEATING  AND  VENTILATION 


above.     Figs.  152  and  153  show  common  forms  of  fan  engines.     The 
latter  is  especially  adapted  to  this  purpose,  as  all  bearings  are  enclosed 


Fig.  152,    A  Common  Form  of  Fan  Engine. 

and  protected  from  dust  and  grit.     A  horizontal  engine  for  fan  use 
is  shown  in  Fig.  154. 

In  case  an  engine  is  belted,  the  distance  between  the  shafts  of 
the  fan  and  engine  should  not  in  general  be  much  less  than  10  feet 


HEATING  AND  VENTILATION 


177 


for  fans  up  to  7  or  8  feet  in  diameter,  and  12  feet  for  those  of  larger 
size.  When  possible,  the  tight  or  driving  side  of  the  belt  should 
be  at  the  bottom,  so  that  the  loose  side,  coming  on  top,  will  tend  to 
wrap  around  the  pulleys  and  so  increase  the  arc  of  contact. 

Motors.     Electric   motors   are   especially   adapted   for  use   in 
connection  with  fans.     This  method  of  driving  is  more  expensive 


Fig.  153.    Another  Form  of  Fan  Engine,  with  Bearings  Enclosed  to  Protect  Them 
from  Dust  and  Grit. 

than  by  the  use  of  an  engine,  especially  if  electricity  must  be  pur- 
chased from  outside  parties;  but  if  the  building  contains  its  own 
power  plant,  so  that  the  exhaust  steam  can  be  utilized  for  heating, 
the  convenience  and  simplicity  of  motor-driven  fans  often  more  than 
offset  the  additional  cost  of  operation. 


178 


HEATING  AND  VENTILATION 


Direct-connected  motors  are  always  preferable  to  belted,  if  a 
direct  current  is  available,  on  account  of  greater  quietness  of  action. 
This  is  due  both  to  the  slower  speed  of  the  motor  and  to  the  absence 
of  belts. 

Sufficient  speed  regulation  can  be  obtained  with  direct -connected 
machines,  without  excessive  waste  of  energy,  by  the  use  of  a  rheostat. 

If  a  direct  current  is  not  available,  and  an  alternating  current 
must  be  used,  the  advantages  of  electric  driving  are  greatly  reduced, 
as  high-speed  motors  with  belts  must  be  employed,  and,  further- 
more, satisfactory  speed  regulation  is  not  easily  attainable. 


Fig.  154.    Horizontal  Engine  for  Fan  Use, 

Area  of  Ducts  and  Flues.  With  the  blower  type  of  fan,  the  size 
of  the  main  ducts  may  be  based  on  a  velocity  of  1,200  to  1,500  feet  per 
minute;  the  branches,  on  a  velocity  of  1,000  to  1,200  feet  per  minute, 
and  as  low  as  600  to  800  feet  when  the  pipes  are  small.  Flue  veloci- 
ties of  500  to' 700  feet  per  minute  may  be  used,  although  the  lower 
velocity  is  preferable.  The  size  of  the  inlet  register  should  be  such 
that  the  velocity  of  the  entering  air  will  not  exceed  about  300  feet  per 
minute.  The  velocity  between  the  inlet  windows  and  the  fan  or 
heater  should  not  exceed  about  800  feet. 

The  air-ducts  and  flues  are  usually  made  of  galvanized  iron,  the 


HEATING  AND  VENTILATION 


179 


ducts  being  run  at  the  basement  ceiling.     No.  20  and  No.  22  iron 
is  used  for  the  larger  sizes,  and  No.  24  to  No.  28  for  the  smaller. 

Regulating  dampers  should 
be  placed  in  the  branches  lead-  «- 
ing  to  each  flue,  for- increasing  or 
reducing  the  air-supply  to  the 
different  rooms.  Adjustable  de- 
flectors are  often  placed  at  the 
fork  of  a  pipe  for  the  same  pur- 
pose. One  of  these  is  shown  in 
Fig.  155. 

Fig.  156  illustrates  a    com- 
mon   arrangement    of    fan    and 
heater  where  the  type  of  heater  Fig.155.  Adjustable  Deflector  Placed  at  Fork 
shown  in  Fig.  138  is  used;  and  o  Regulate  Air-suppiy. 

Fig.  157  is  a  self-contained  apparatus  in  which  the  heater  is  inclosed 

in  a  steel  casing. 

Factory    Heating.    The    application    of   forced    blast    for   the 

warming  of  factories  and 
shops,  is  shown  in  Figs. 
158  and  159.  The  pro- 
portional heating  surface 
in  this  case  is  generally 
expressed  in  the  number 
of  cubic  feet  in  the 
building  for  each  linear 
foot  of  1-inch  steam 
pipe  in  the  heater.  On 
this  basis,  in  factory 
practice,  with  all  of  the 
air  taken  from  out  of 
doors,  there  are  generally 
allowed  from  100  to  150 
cubic  feet  of  space  per 


COLD   AtP 


XXXXXXXX 


1  HEAT/NG  CO/LS    * 

V  I 


m 


DUCT  fWJff 
BLOWffl  ATCf/UNB 


Fig.  156 


&4-UWCK    I/     C*£V£.//TC»  -  I*  •  1* 

.    Common  Arrangement  of  Fan  with  Heater       *<**  of  pipe,  according  as 


of  Type  shown  in  Fig.  138 


exhaust    or    live    steam 


is    used,    live    steam    in    this  case   indicating  steam  of   about   80 
pounds  pressure.     If  practically  all  the  air  is  returned  from  the 


180 


HEATING  AND  VENTILATION 


buildings  to  the  heater,  these  figures  may  be  raised  to  about  140  as  a 
minimum,  and  possibly  200  as  a  maximum,  per  foot  of  pipe.    The 


heaters  in  Table  XXXI  may  be  changed  to  linear  feet  of  1  inch  pipe 
by  multiplying  the  numbers  in  column  three  (sauare  feet  of  surface) 
by  three. 


HEATING  AND  VENTILATION 


181 


EXAMPLES  FOR  PRACTICE 


1.     A  machine  shop  100  feet  long  by  50  feet  wide  and  having  3 
stories,  each  10  feet  high,  is  to  be  warmed  by  forced  blast,  using 


Fig.  158.    Illustrating  Application  of  Forced  Blast  for  Warming  a  Factory. 

exhaust  steam  in  the  heater.  The  air  is  to  be  returned  to  the  heater 
from  the  building,  and  the  whole  amount  contained  in  the  building 
is  to  pass  through  the  heater  every  15  minutes. 


What  size  of  blower 


182 


HEATING  AND  VENTILATION 


will  be  required,  and  what  will  be  the  H.  P.  of  the  engine  required  to 
run  it?  How- many  linear  feet  of  1-inch  pipe  should  the  heater  con- 
tain? 

{4-foot   blower. 
6  H.  P.  engine. 
1,071   feet  of  pipe. 


Fig.  159.    Centrifugal  Blower  Producing  Forced  Blast  for  Heating  a  Shop. 

2.  Find  the  size  of  blower,  engine,  and  heater  for  a  factory 
200  feet  long,  60  feet  wide,  and  having  4  stories,  each  10  feet  high, 
using  live  steam  at  80  pounds  pressure  in  the  heater,  and  changing 
the  air  every  20  minutes  by  taking  in  cold  air  from  out  of  doors. 

I  6-foot  blower. 
ANS.  1  13  H.  P.  engine. 

[3,200  feet  of  pipe, 


HEATING  AND  VENTILATION 


183 


In  using  this  method  of  computation,  judgment  must  be  employed, 
which  can  come  only  from  experience.  The  figures  given  are  for 
average  conditions  of  construction  and  exposure. 

Double=Duct  System.  The  varying  exposures  of  the  rooms  of 
a  school  or  other  building  similarly  occupied,  rejquire  that  more  heat 
shall  be  supplied  to  some  than  to  others.  Rooms  that  are  on  the 
south  side  of  the  building  and  exposed  to  the  sun,  may  perhaps  be 
kept  perfectly  comfortable  with  a  supply  of  heat  that  will  maintain 
a  temperature  of  only  50  or  60  degrees  in  rooms  on  the  opposite  side 
of  the  building  which  are  exposed  to  high  winds  and  shut  off  from  the 
warmth  of  the  sun. 


Fig.  160.    Hot-Blast  Apparatus  with  Double  Duct  for  Supplying  Air  at  Different  Temper- 
atures to  Different  Parts  of  a  Building. 

With  a  constant  and  equal  air-supply  to  each  room,  it  is  evident 
that  the  temperature  must  be  directly  proportional  to  the  cooling 
surfaces  and  exposure,  and  that  no  building  of  this  character  can  be 
properly  heated  and  ventilated  if  the  temperature  cannot  be  varied 
without  affecting  the  air-supply. 

There  are  two  methods  of  overcoming  this  difficulty: 
The  older  arrangement  consists  in  heating  the  air  by  means  of  a 
primary  coil  at  or  near  the  fan,  to  about  60  degrees,  or  to  the  minimum 
temperature  required  within  the  building.  From  the  coil  it  passes 
to  the  bases  of  the  various  flues,  and  is  there  still  further  heated  as 
required,  by  secondary  or  supplementary  heaters  placed  at  the  base  of 
each  flue. 


184 


HEATING  AND  VENTILATION 


With  the  second  and  more  recent  method,  a  single  heater  is 
employed,  and  all  the  air  is  heated  to  the  maximum  required  to 
maintain  the  desired  temperature  in  the  most  exposed  rooms,  while 
the  temperature  of  the  other  rooms  is  regulated  by  mixing  with  the 
hot  air  a  sufficient  volume  of  cold  air  at  the  bases  of  the  different  flues. 
This  result  is  best  accomplished  by  designing  a  hot-blast  apparatus 

so  that  the  air  shall  be 
forced,  rather  than  drawn 
through  the  heater,  and 
by  providing  a  by-pass 
through  which  it  may 
be  discharged  without 
passing  across  the  heated 
pipes. 

The  passage  for  the 
cool  air  is  usually  above 
and  separate  from  the 
heater  pipes,  as  shown  in 
Fig.  160.  Extending 
from  the  apparatus  is  a 
double  system  of  ducts, 
usually  of  galvanized 
iron,  suspended  from  the 
ceiling.  At  the  base  of 
each  flue  is  placed  a  mix- 
ing damper,  which  is 
controlled  by  a  chain 
from  the  room  above, 
and  so  designed  as  to 
admit  either  a  full  vol- 
ume of  hot  air,  a  full 
volume  of  cool  or 

tempered  air,  or  to  mix  them  in  any  desired  proportion  without  affect- 
ing the  resulting"  total  volume  delivered  to  the  room.     A  damper  o 
this  form  is  shown  in  Fig.  161. 

Fig.  162  shows  an  arrangement  of  disc  fan  and  heater  where  the 
air  is  first  drawn  through  a  tempering  coil,  then  a  portion  of  it  forced 
through  a  second  heater  and  into  the  warm-air  pipes,  while  the  remain- 


Fig.  161.    Mixing  Damper  for  Regulating  Temperature 
of  Air  Supplied  by  Double-Duct  System. 


HEATING  AND  VENTILATION 


185 


der  is  by-passed  under  the  heater  into  the  cold-air  pipes.     Mixing 

3 


dampers  are  placed  at  the  bases  of  the  flues  as  already  described,  to 
regulate  the  temperature  in  different  rooms. 


186  HEATING  AND  VENTILATION 

ELECTRIC  HEATING 

Unless  electricity  is  produced  at  a  very  low  cost,  it  is  not  com- 
mercially practicable  for  heating  residences  or  large  buildings.  The 
electric  heater,  however,  has  quite  a  wide  field  of  application  in  heating 
small  offices,  bathrooms,  electric  cars,  etc.  It  is  a  convenient  method 
of  warming  rooms  on  cold  mornings  in  late  spring  and  early  fall, 
when  furnace  or  steam  heat  is  not  at  hand.  It  has  the  special  advan- 
tage of  being  instantly  available,  and  the  amount  of  heat  can  be  regu- 
lated at  will.  The  heaters  are  perfectly  clean,  do  not  vitiate  the  air, 
and  are -portable. 

Electric  Heat  and  Energy.  The  commercial  unit  for  electricity 
is  one  watt  for  one  hour,  and  is  equal  to  3.41  B.  T.  U.  Electricity  is 
usually  sold  on  the  basis  of  1,000  watt-hours  (called  Kilowatt-hours), 


Fig.  163.    Electric  Car-Heater. 

which  is  equivalent  to  3,410  B.  T.  U.  A  watt  is  the  product  obtained 
by  multiplying  a  current  of  1  ampere  by  an  electromotive  force  of  1 
volt. 

From  the  above  we  see  that  the  B.  T.  U.  required  per  hour  for 
warming,  divided  by  3,410,  will  give  the  kilowatt-hours  necessary  for 
supplying  the  required  amount  of  heat. 

Construction  of  Electric  Heaters.  Heat  is  obtained  from  the 
electric  current  by  placing  a  greater  or  less  resistance  in  its  path. 
Various  forms  of  heaters  have  been  employed.  Some  of  the  simplest 
consist  merely  of  coils  or  loops  of  iron  wire,  arranged  in  parallel  rows, 
so  that  the  current  can  be  passed  through  as  many  coils  as  are  needed 
to  provide  the  required  amount  of  heat.  In  other  forms,  the  heating 
material  is  surrounded  with  fire-clay,  enamel,  or  asbestos,  and  in  some 
cases  the  material  itself  has  been  such  as  to  give  considerable  resist- 
ance to  the  current.  A  form  of  electric  car-heater  is  shown  in  Fig.  163. 
Forms  of  radiators  are  shown  in  Figs.  164  and  165. 


HEATING  AND  VENTILATION 


187 


Calculation  of  Electric  Heaters.    The  formula  for  the  calcu- 
lation of  electric  heaters  is 


H  =  I2  R  t  x  .24, 


in  which 


H  =  Heat,  in  calories; 

7  =  Current,  in  amperes; 
R  =  Resistance,  in  ohms; 

t  =  Time,  in  seconds. 

Examples.  What  resistance  must  an 
electric  heater  have,  to  give  off  6,000  B. 
T.  U.  per  hour,  with  a  current  of  20  am- 
peres ? 

We  have  learned  that  1  B.  T.  U.   =  =   252  calories;  so,  in  the 
present  case,  6,000  X   252  =  1,512,000  calories  must  be  provided. 
Substituting  the  known  values  in  the  formula,  we  have 

1,512,000  =  202  X  -R  X  3,600  X  .24, 
from  which 

1,512;000 


Fig.  164.    Electric  Radiator. 


R  = 


=  4.37  ohms. 


345,600 

A  heater  having  a  resistance  of  3  ohms  is  to  supply  3,000  B.  T.  U.  per 
hour.     What  current  will  be  required  ? 


Fig.  165.    Another  Form  of  Electric  Radiator. 

3,000  X  252  =  756,000  calories.     Substituting  the  known  values  in 
the  formula,  and  solving  for  /,  we  have 

756,000  =  P  X  3  X  3,600  X  .24, 
from  which 

7  =  i/  291.6  =17  +  amperes. 

Connections  for  Electric  Heaters.  The  method  of  wiring  for 
electric  heaters  is  essentially  the  same  as  for  lights  which  require  the 
same  amount  of  current.  A  constant  electromotive  force  or  voltage 


188  HEATING  AND  VENTILATION 


is  maintained  in  the  main  wire  leading  to  the  heaters.  A  much  less 
voltage  is  carried  on  the  return  wire,  and  the  current  in  passing  through 
the  heater  from  the  main  to  the  return,  drops  in  voltage  or  pressure. 
This  drop  provides  the  energy  which  is  transformed  into  heat. 

The  principle  of  electric  heating  is  much  the  same  as  that  in- 
volved in  the  non-gravity  return  system  of  steam  heating.  In  that 
system,  the  pressure  on  the  main  steam  pipes  is  that  of  the  boiler, 
while  that  on  the  return  is  much  less,  the  reduction  in  pressure  occur- 
ring in  the  passage  of  the  steam  through  the  radiators;  the  water  of 
condensation  is  received  into  a  tank,  and  returned  to  the  boiler  by  a 
pump. 

In  a  system  of  electric  heating,  the  main  wires  must  be  suffi- 
ciently large  to  prevent  a  sensible  reduction  in  voltage  or  pressure 
between  the  generator  and  the  heater,  so  that  the  pressure  in  them 
shall  be  .substantially  that  in  the  generator.  The  pressure  or  voltage 
in  the  main  return  wire  is  also  constant,  but  very  low,  and  the  genera- 
tor has  an  office  similar  to  that  of  the  steam  pump  in  the  system  just 
described — that  is,  of  raising  the  pressure  of  the  return  current  up 
to  that  in  the  main.  The  power  supplied  to  the  generator  can  be 
considered  the  same  as  the  boiler  in  the  first  case.  All  the  current 
which  passes  from  the  main  to  the  return  must  flow  through  the  heater, 
and  in  so  doing  its  pressure  or  voltage  falls  from  that  of  the  main 
to  that  of  the  return. 

From  the  generator  shown  in  Fig.  166,  main  and  return  wires 
are  run  the  same  as  in  a  two-pipe  system  of  steam  heating,  and  these 
are  proportioned  to  carry  the  required  current  without  sensible  drop 
or  loss  of  pressure.  Between  these  wires  are  placed  the  various 
heaters,  which  are  arranged  so  that  when  electric  connection  is  made 
they  draw  the  current  from  the  main  and  discharge  it  into  the  return 
wire.  Connections  are  made  and  broken  by  switches,  which  take  the 
place  of  valves  on  steam  radiators. 

Cost  of  Electric  Heating.  The  expense  of  electric  heating  must 
in  every  case  be  great,  unless  the  electricity  can  be  supplied  at  an 
exceedingly  low  cost.  Estimated  on  the  basis  of  present  practice, 
the  average  transformation  into  electricity  does  not  account  for  more 
than  4  per  cent  of  the  energy  in  the  fuel  which  is  burned  in  the  furnace. 
Although  under  best  conditions  15  per  cent  has  been  realized,  it 
would  not  be  safe  to  assume  that  in  ordinary  practice  more  than  5 


HEATING  AND  VENTILATION 


189 


per  cent  could  be  transformed  into  electrical  energy.  In  heating 
with  steam,  hot  water,  or  hot  air,  the  average  amount  utilized  will 
probably  be  about  60  per  cent,  so  that  the  expense  of  electrical  heating 
is  approximately  from  12  to  15  times  greater  than  by  these  methods. 

TEMPERATURE  REGULATORS 

The  principal  systems  of  automatic  temperature  control  now  in 
use,  consist  of  three  essential  features;  First,  an  air-compressor, 
reservoir,  and  distributing  pipes;  second,  thermostats,  which  are 


Fig.  166.    General  System  of  Wiring  a  House  for  Electric  Heating. 

placed  in  the  rooms  to  be  regulated;  and  third,  special  diaphragm  or 
pneumatic  valves  at  the  radiators. 

The  air-compressor  is  usually  operated  by  water-pressure  in 
small  plants  and  by  steam  in  larger  ones;  electricity  is  used  in  some 
cases.  Fig.  167  shows  a  form  of  water  compressor.  It  is  similar 
in  principle  to  a  direct-acting  steam  pump,  in  which  water  under 
pressure  takes  the  place  of  steam.  A  piston  in  the  upper  cylinder 
compresses  the  air,  which  is  stored  in  a  reservoir  provided  for  the 
purpose.  When  the  pressure  in  the  reservoir  drops  below  a  certain 


190 


HEATING  AND  VENTILATION 


point,   the  compressor  is  started   automatically,   and  continues  to 
operate  until  the  pressure  is  brought  up  to  its  working  standard. 

A  thermostat  is  simply  a  mechanism  for  opening  and  closing 
one  or  more  small  valves,  and  is  actuated  by  changes  in  the  tempera- 


Fig.  167.  Air-Compressor  Operated  by  Wa- 
ter-Pressure, Automatically  Controlled, 
and  Operating  to  Regulate  Temperature 
by  Controlling  Radiator  Valves. 


Fig.  168.  Thermostat  Controlling  Valves 
on  Radiators,  and  Operating  through  Ex- 
pansion or  Contraction  of  Metal  Strip  E. 


ture  of  the  air  in  which  it  is  placed.  Fig.  168  shows  a  thermostat 
in  which  the  valves  are  operated  by  the  expansion  and  contraction 
of  the  metal  strip  E.  The  degree  of  temperature  at  which  it  acts 
may  be  adjusted  by  throwing  the  pointer  at  the  bottom  one  way  or 
the  other.  Fig.  169  shows  the  same  thermostat  with  its  ornamental 


HEATING  AND  VENTILATION 


191 


casing  in  place.  The  thermostat  shown  in  Fig.  170  operates  on 
a  somewhat  different  principle.  It  consists  of  a  vessel  separated  into 
two  chambers  by  a  metal  diaphragm. 
One  of  these  chambers  is  partially 
filled  with  a  liquid  which  will  boil 
at  a  temperature  below  that  desired 
in  the  room.  The  vapor  of  the 
liquid  produces  considerable  pres- 
sure at  the  normal  temperature  of 
the  room,  and  a  slight  increase  of 
heat  crowds  the  diaphragm  over 
and  operates  the  small  valves  in  a 
manner  similar  to  that  of  the  metal 
strip  in  the  case  just  described. 

The  general  form  of  a  dia- 
phragm  valve  is  shown  in  Fig.  171. 
These  replace  the  usual  hand-valves 
at  the  radiators.  They  are  similar 
in  construction  to  the  ordinary 
globe  or  angle  valve,  except  that 
the  stem  slides  up  and  down  in- 
stead of  being  threaded  and  run- 
ning in  a  nut.  The  top  of  the  stem 
connects  with  a  flat .  plate,  which 
rests  against  a  rubber  diaphragm. 
The  valve  is  held  open  by  a  spring, 
as  shown,  and  is  closed  by  admit- 
ting compressed  air  to  the  space 
above  the  diaphragm. 

In  connecting  up  the  system, 
small  concealed  pipes  are  carried 
from  the  air-reservoir  to  the  ther- 
mostat, which  is  placed  upon  an 
inside  wall  of  the  room,  and  from 
there  to  the  diaphragm  valve  at 
the  radiator.  When  the  temperature  of  the  room  reaches  the  maxi- 
mum point  for  which  the  thermostat  is  set,  its  action  opens  a  small 
valve  and  admits  air-pressure  to  the  diaphragm,  thus  closing  off  the 


Fig.  169.    Thermostat  of  Fig.  168  in 
Ornamental  Casing. 


192  HEATING  AND  VENTILATION 

steam  from  the  radiator.  When  the  temperature  falls,  the  thermostat 
acts  in  the  opposite  manner,  and  shuts  off  the  air-pressure  from  the 
diaphragm  valve,  at  the  same  time  opening  a  small  exhaust  which 
allows  the  air  above  the  diaphragm  to  escape.  The  pressure  being 
removed,  the  valve  opens  and  again  admits  steam  to  the  radiator. 

Diaphragm  Motors.  Dampers  are  operated  pneumatically  in 
a  similar  manner  to  steam  valves.  A  diaphragm  motor,  so  called,  is 
acted  upon  by  the  air-pressure;  and  this  lifts  a  lever  which  is  properly 
connected  to  the  damper  by  means  of  chains  or  levers,  thus  securing 
the  desired  movement. 

Dampers.  When  mixing  dampers  are  operated  pneumatically, 
a  specially  designed  thermostat  for  giving  a  graduated  movement 


i 


Fig  170     Thermostat  Operating  through  Expansion  or  Contraction  of  the  Vapor 
of  a  Volatile  Liquid. 

to  the  damper  should  be  used.  By  this  arrangement  the  damper 
is  held  in  such  a  position  at  all  times  as  to  admit  the  proper  proportions 
of  hot  and  cold  or  tempered  air  for  producing  the  desired  temperature 
in  the  room  with  which  it  is  connected. 

Large  dampers  which  are  to  be  operated  pneumatically,  should 
be  made  up  in  sections  or  louvres.  Dampers  constructed  in  this 
manner  are  handled  much  more  easily  than  when  made  in  a  single 
piece. 

It  often  happens,  in  large  plants,  that  there  are  valves  and 
dampers  in  places  which  are  not  easily  reached  for  hand  manipula- 
tion. These  may  be  provided  with  diaphragms  and  connected  with 
the  air-pressure  system  for  operation  by  hand -switches  or  cocks 


HEATING  AND  VENTILATION 


193 


conveniently  located  at  some  centraf  point  in  the  basement  or  boiler 
room. 

Telethermometer.  This  is  a  device  for  indicating  on  a  dial 
at  some  central  point  the  temperature  of  various  rooms  or  ducts  in 
different  parts  of  a  buiMing.  A  special  transmitter  is  placed  in  each 
of  the  rooms  and  electrically  connected  with  a  central  switchboard. 
Then,  by  means  of  suitable  switches,  any  room  may  be  thrown  in 
circuit  with  the  recorder,  and  the  temperature  existing  in  the  room 
at  that  time  read  from  the  dial. 


Fig.  171.    Exterior  View,  and  Section  Showing  Interior  Mechanism  of  Diaphragm  Valve. 

Humidostat.  The  humidostat  is  a  device  to  be  placed  in  one  or 
more  rooms  of  a  building  for  maintaining  an  even  percentage  of 
moisture  in  the  air.  The  apparatus  consists  of  two  essential  parts — 
the  humidostat  and  the  humidifier.  The  former  corresponds  to  the 
thermostat  in  a  system  of  temperature  control,  and  operates  a  pneu- 
matic valve  or  other  mechanism  connected  with  the  humidifier  when 
the  percentage  of  moisture  rises  above  or  falls  below  certain  limits. 
The  operating  medium  is  compressed  air,  the  same  as  for  tempera- 
ture control ;  and  the  two  devices  are  usually  connected  with  the  same 
pressure  system. 


194  HEATING  AND  VENTILATION 

The  normal  moisture  of  a  room  is  70  per  cent,  and  should  never 
exceed  that.  In  cold  weather  it  will  be  necessary  to  reduce  the 
amount  of  moisture  somewhat,  owing  to  the  "sweating"  of  walls  and 
windows. 

The  method  of  moistening  the  air  will  depend  somewhat  upon 
circumstances.  If  the  air  for  ventilation  is  delivered  to  the  rooms  at 
a  temperature  not  exceeding  70  degrees,  the  humidifier  is  best  placed 
in  the  main  air-duct.  If  the  air  enters  at  a  higher  temperature,  the 
humidifier  must  be  located  in  the  same  room  with  the  humidostat. 

The  moistener  or  humidifier  may  be  of  any  one  of  several  forms. 
Where  steam  heating  is  used,  and  where  the  steam  is  clean  and  odor- 
less and  free  from  oil  from  engines,  a  perforated  pipe  (or  pipes)  in  the 
air-duct  is  the  simplest  and  best  humidifier.  The  outlets  are  properly 
adjusted,  and  then  the  humidostat  shuts  off  and  lets  on  the  steam 
as  required.  Sometimes  a  water  spray,  particularly  of  warm  water, 
may  be  used  in  place  of  steam.  When  neither  steam  jet  nor  water 
spray  is  advisable,  an  evaporating  pan  containing  a  steam  coil  may 
be  used,  the  humidostat  controlling  the  steam  to  the  coil,  and  the 
water-level  in  the  pan  being  kept  constant  by  means  of  a  ball-cock. 

AIR=FILTERS  AND  AIR-WASHERS 

In  cases  where  the  air  for  ventilating  purposes  is  likely  to  contain 
soot  or  street  dust,  it  is  desirable  to  provide  some  form  of  filter  for 
purifying  it  before  delivering  to  the  rooms.  If  the  air-quantity  is 
small  and  there  is  plenty  of  room  between  the  inlet  windows  and 
the  fan,  screens  of  light  cheesecloth  may  be  used  for  this  purpose. 
The  cloth  should  be  tacked  to  light  but  substantial  wooden  frames, 
which  can  be  easily  removed  for  frequent  cleaning.  These  screens  are 
usually  set  up  in  "saw -tooth"  fashion  in  order  to  give  as  much  sur- 
face as  possible  in  the  least  space. 

Another  arrangement,  used  in  case  of  large  volumes  of  air, 
is  to  provide  a  number  of  light  cloth  bags  of  considerable  length, 
through  which  the  air  is  drawn  before  reaching  the  heater.  These  are 
fastened  to  a  suitable  frame  or  partition  for  holding  them  open.  The 
great  objection  to  filters  of  this  kind  is  their  obstruction  to  the  passage 
of  the  air,  especially  when  filled  with  dust,  the  frequent  intervals  at 
which  they  should  be  cleaned,  and  the  great  amount  of  filtering  sur- 
face required. 


HEATING  AND  VENTILATION 


195 


An  apparatus  which  is 
coming  quite  generally  into 
use  for  this  purpose,  and 
which  does  away  with  the 
disadvantages  noted  above, 
is  the  spray  filter  or  air- 
washer,  one  form  of  which 
is  shown  in  Fig.  172.  Air 
enters  as  indicated,  and 
first  passes  through  a  tem- 
pering coil  to  raise  it  above 
the  freezing  point  in  win- 
ter weather;  then  passes 
through  the  spray-chamber, 
where  the  dirt  is  removed; 
then  through  an  eliminator 
for  removing  the  water; 
and  then  through  a  second 
heater  on  its  vray  to  the 
fan. 

The  water  is  forced 
through  the  spray-heads 
by  means  of  a  small  cen- 
trifugal pump,  either  belted 
to  the  fan  shaft  or  driven 
by  an  independent  motor. 

HEATING  AND 
VENTILATION  OF 
VARIOUS  CLASSES 
OF  BUILDINGS 

The  different  methods 
used  in  heating  and  venti- 
lation, together  with  the 
manner  of  computing  the 
various  proportions  of  the 
apparatus,  having  been 


196  HEATING  AND  VENTILATION 

taken  up,  the  application  of  these  systems  to  the  different  classes 
of  buildings  will  now  be  considered  briefly. 

School  Buildings.  For  school  buildings  of  small  size,  the  furnace 
system  is  simple,  convenient,  and  generally  effective.  Its  use  is  con- 
fined as  a  general  rule  to  buildings  having  not  more  than  six  or  eight 
rooms .  For  large  ones  this  method  must  generally  give  way  to  some 
form  of  indirect  steam  system  with  one  or  more  boilers,  which  occupy 
less  space,  and  are  more  easily  cared  for  than  a  number  of  furnaces 
scattered  about  in  different  parts  of  the  basement.  As  in  all  systems 
that  depend  on  natural  circulation,  the  supply  and  removal  of  air  is 
considerably  affected  by  changes  in  the  outside  temperature  and  by 
winds. 

The  furnaces  used  are  generally  built  of  cast  iron,  this  material 
being  durable,  and  easily  made  to  present  large  and  effective  heating 
surfaces.  To  adapt  the  larger  sizes  of  house-heating  furnaces  to 
schools,  a  much  larger  space  must  be  provided  between  the  body  and 
the  casing,  to  permit  a  sufficient  volume  of  air  to  pass  to  the  rooms. 
The  free  area  of  the  air-passage  should  be  sufficient  to  allow  a  velocity 
of  about  400  feet  per  minute. 

The  size  of  furnace  is  based  on  the  amount  of  heat  lost  by  radia- 
tion and  conduction  through  walls  and  windows,  plus  that  carried 
away  by  air  passing  up  the  ventilating  flues.  These  quantities  may 
be  computed  by  the  usual  methods  for  "loss  of  heat  by  conduction 
through  walls/'  and  "heat  required  for  ventilation."  With  more 
regular  and  skilful  attendance,  it  is  safe  to  assume  a  higher  rate  of 
combustion  in  schoolhouse  heaters  than  in  those  used  for  warming 
residences.  Allowing  a  maximum  combustion  of  6  pounds  of  coal 
per  hour  per  square  foot  of  grate,  and  assuming  that  8,000  B.  T.  U. 
per  pound  are  taken  up  by  the  air  passing  over  the  furnace,  we  have 
6  X  8,000  =  48,000  B.  T.  U.  furnished  per  hour  per  square  foot  of 
grate.  Therefore,  if  we  divide  the  total  B.  T.  U.  required  for  both 
warming  and  ventilation  by  48,000,  it  will  give  us  the  necessary  grate 
surface  in  square  feet.  It  has  been  found  in  practice  that  a  furnace 
with  a  firepot  32  inches  in  diameter,  and  having  ample  heating  surface, 
is  capable  of  heating  two  50-pupil  rooms  in  zero  weather.  The  sizes 
of  ducts  and  flues  may  be  determined  by  rules  already  given  under 
furnace  and  indirect  steam  heating. 

The  velocity  of  the  warm  air  within  the  uptake  flues  depends 


HEATING  AND  VENTILATION  197 

upon  their  height  and  the  difference  in  temperature  between  the 
warm  air  within  the  flues  and  the  cold  air  outside.  The  action  of 
the  wind  also  affects  the  velocity  of  air-flow.  It  has  been  found  by 
experience  that  flues  having  sectional  areas  of  about  6  square  feet  for 
first-floor  rooms,  5  squaje  feet  for  the  second  floor,  and  4J  square  feet 
for  the  third,  will  be  of  ample  size  for  standard  classrooms  seating 
from  40  to  50  pupils  in  primary  and  grammar  schools.  These  sizes 
may  be  used  for  both  furnace  and  indirect  gravity  steam  heating. 

The  vent  flues  may  be  made  5  square  feet  for  the  first  floor,  and 
6  square  feet  for  the  second  and  third  floors.  They  may  be  ar- 
ranged in  banks,  and  carried  through  the  roof  in  the  form  of  large 
chimneys,  or  may  be  carried  to  the  attic  space  and  there  gathered 
by  means  of  galvanized-iron  ducts  connecting  with  roof  vents  of 
wood  or  copper  construction. 

In  order  to  make  the  vent  flues  "draw"  sufficiently  in  mild  or 
heavy  weather,  it  is  necessary  to  provide  some  means  for  warming 
the  air  within  them  to  a  temperature  somewhat  above  that  of  the 
rooms  with  which  they  connect.  This  may  be  done  by  placing  a 
small  stove  made  specially  for  the  purpose,  at  the  base  of  each  flue. 
If  this  is  done,  it  is  necessary  to  carry  the  air  down  and  connect  with 
the  flue  just  below  the  stove. 

The  cold-air  supply  duct  to  each  furnace  should  be  made  f 
the  size  of  all  the  warm-air  flues  if  free  from  bends,  or  the  full 
size  if  obstructed  in  any  way. 

The  inlet  and  outlet  openings  from  the  rooms  into  the  flues,  are 
commonly  provided  with  grilles  of  iron  wire  having  a  mesh  of  2  to  2V 
inches.  Both  flat  and  square  wire  are  used  for  this  purpose.  Mixing 
dampers  for  regulating  the  temperature  of  the  rooms  should  be  pro- 
vided for  each  flue.  The  effectiveness  of  these  dampers  will  depend 
largely  upon  their  construction;  and  they  should  be  made  tight 
against  cold-air  leakage,  by  covering  the  surfaces  or  flanges  against 
which  they  close  with  some  form  of  asbestos  felting.  Both  inlet  and 
outlet  gratings  should  be  provided  with  adjustable  dampers.  One  of 
the  disadvantages  of  this  system  is  the  delivery  of  all  the  heat  to  the 
room  from  a  single  point,  and  this  not  always  in  a  position  to  give  the 
best  results.  The  outer  walls  are  thus  left  unwarmed,  except  as  the 
heat  is  diffused  throughout  the  room  by  air-currents.  When  there  is 
considerable  glass  surfaqe,  as  in  most  of  our  modern  schoolrooms, 


198  HEATING  AND  VENTILATION 

draughts  and  currents  of  cold  air  are  frequently  found  along  the  out- 
side walls. 

The  indirect  gravity  system  of  steam  heating  comes  next  in  cost 
of  installation.  One  important  advantage  of  this  system  over  furnace 
heating  comes  from  the  ability  to  place  the  heating  coils  at  the  base 
of  the  flues,  thus  doing  away  with  horizontal  runs  of  air-pipe,  which 
are  required  to  some  extent  in  furnace  heating.  The  warm-air 
currents  in  the  flues  are  less  affected  by  variations  in  the  direction  and 
force  of  the  wind  where  this  construction  is  possible,  and  this  is  of 
much  importance  in  exposed  locations. 

The  method  of  supplying  cold  air  to  the  coils  or  heaters  is  im- 
portant, and  should  be  carefully  worked  out.  The  supply  should  be 
taken  from  at  least  two  sides  of  the  building,  or,  if  possible,  from  all 
four  sides.  When  it  is  taken  from  four  sides,  each  inlet  should  be 
made  large  enough  to  supply  one-half  the  amount,  or,  in  other  words, 
any  two  should  give  the  total  quantity  required.  It  is  often  possible 
to  arrange  the  flues  in  groups  so  that  all  the  heating  stacks  may  be 
placed  in  two  or  more  cold-air  chambers,  depending  upon  the  size 
of  the  building.  A  cold-air  trunk  line  may  be  run  through  the  center 
of  the  basement,  connecting  with  the  outside  on  all  four  sides,  and 
having  branches  supplying  each  cold-air  chamber. 

Cast-iron  pin-radiators  are  particularly  adapted  to  this  class 
of  work. 

The  School-Pin,  having  a  section  about  10  inches  in  depth  and 
rated  at  15  square  feet  of  heating  surface  per  section,  is  used  quite 
extensively  for  this  purpose.  Stacks  containing  about  240  square 
feet  of  surface  for  southerly  rooms,  and  260  for  those  having  a  north- 
erly exposure,  have  been  found  ample  for  ordinary  conditions  in  zero 
weather. 

A  very  satisfactory  arrangement  is  the  use  of  indirect  heaters 
for  warming  the  air  needed  for  ventilation,  and  the  placing  of  direct 
radiation  in  the  rooms  for  heating  purposes.  The  general  construc- 
tion of  the  indirect  stacks  and  flues  may  be  the  same ;  but  the  heating 
surface  can  be  reduced,  as  the  air  in  this  case  must  be  raised  only  to 
70  or  75  degrees  in  zero  weather,  the  heat  to  offset  that  lost  by  con- 
duction, etc.,  through  walls  and  windows  being  provided  by  the 
direct  surface.  The  mixing  dampers  may  be  omitted,  and  the  tem- 
perature of  the  room  regulated  by  opening  or  closing  the  steam  valves 


HEATING  AND  VENTILATION  199 

on  the  direct  coils,  which  should  be  done  automatically.  The  direct- 
heating  surface,  which  is  best  made  up  of  lines  of  1^-inch  pipe,  should 
be  placed  along  the  outer  walls  beneath  the  windows  This  supplies 
heat  where  most  needed,  and  does  away  with  the  tendency  to  draughts. 
In  mild  weather,  during  the  spring  and  fall,  the  indirect  heaters  may 
prove  sufficient  for  both  ventilation  and  warming. 

Where  direct  radiation  is  placed  in  the  rooms,  the  quantity  of 
heat  supplied  is  not  affected  by  varying  wind  conditions,  as  is  the 
case  in  indirect  heating.  Although  the  air-supply  may  be  reduced 
at  times,  the  heat  quantity  is  not  changed.  Direct  radiation  has  the 
disadvantage  of  a  more  or  less  unsightly  appearance,  and  architects 
and  owners  often  object  to  the  running  of  mains  or  risers  through 
the  rooms  of  the  building.  Air-valves  should  always  be  provided 
with  drip  connections  carried  to  a  sink  or  dry  well  in  the  basement. 

When  circulation  coils  are  used,  a  good  method  of  drainage  is 
to  carry  separate  returns  from  each  coil  to  the  basement,  and  to  place 
the  air-valves  in  the  drops  just  below  the  basement  ceiling.  A  check- 
valve  should  be  placed  below  the  water-line  in  each  return. 

The  gravity  system  has  the  fault  of  not  supplying  a  uniform 
quantity  of  air  under  all  conditions  of  outside  temperature,  the  same 
as  a  furnace,  but  when  properly  arranged,  may  be  made  to  give  quite 
satisfactory  results. 

The  fan  or  blower  system  for  ventilation,  with  direct  radiation 
in  the  rooms  for  warming,  is  considered  to  be  one  of  the  best  possible 
arrangements. 

In  designing  a  plant  of  this  kind,  the  main  heating  coil  should 
be  of  sufficient  size  to  warm  the  total  air-supply  to  70  or  75  degrees 
in  the  coldest  weather,  and  the  direct  surface  should  be  proportioned 
for  heating  the  building  independently  of  the  indirect  system.  Auto- 
matic temperature  regulation  should  be  used  in  connection  with 
systems  of  this  kind,  by  placing  pneumatic  valves  on  the  direct  radia- 
tion. It  is  customary  to  carry  from  3  to  8  pounds  pressure  on  the 
direct  system,  and  from  8  to  15  pounds  on  the  main  coil,  depending 
upon  the  outside  temperature.  The  foot-warmers,  vestibule,  and 
office  heaters  should  be  placed  on  a  separate  line  of  piping,  with 
separate  returns  and  trap,  so  that  they  can  be  used  independently 
of  the  rest  of  the  building  if  desired.  Where  there  is  a  large  assembly 
hall,  it  should  be  arranged  so  that  it  can  be  both  warmed  and  venti- 


200  HEATING  AND  VENTILATION 

• 

lated  when  the  rest  of  the  building  is  shut  off.  This  can  be  done  by  a 
proper  arrangement  of  valves  and  dampers. 

When  different  parts  of  the  system  are  run  on  different  pressures, 
the  returns  from  each  should  discharge  through  separate  traps  into 
a  receiver  having  connection  with  the  atmosphere  by  means  of  a  vent 
pipe.  Fig.  173  shows  a  common  arrangement  for  the  return  con- 
nections in  a  combination  system  of  this  kind.  The  different  traps 
discharge  into  the  vented  receiver  as  shown;  and  the  water  is  pumped 
back  to  the  boiler  automatically  when  it  rises  above  a  given  level  in 
the  receiver,  a  pump  governor  being  used  to  start  and  stop  the  pumps 
as  required. 

A  water-level  or  seal  of  suitable  height  is  maintained  in  the  main 
returns,  by  placing  the  trap  at  the  required  elevation  and  bringing 
the  returns  into  it  near  the  bottom;  a  balance  pipe  is  connected  with 
the  top  for  equalizing  the  pressure,  the  same  as  in  the  case  of  a  pump 
governor.  Sometimes  a  fan  is  used  with  the  heating  coils  placed  at 
the  base  of  the  flues,  instead  of  in  the  rooms.  Where  this  is  done 
the  radiating  surface  may  be  reduced  about  one-half.  This  system 
is  less  expensive  to  install,  but  has  the  disadvantage  of  removing  the 
heating  surface  from  the  cold  walls,  where  it  is  most  needed. 

With  a  blower  type  of  fan,  the  size  of  the  main  ducts  may  be 
based  on  a  velocity  of  from  1,000  to  1,200  feet  per  minute,  and  the 
branches  on  a  velocity  of  800  to  1,000  feet  per  minute. 

The  velocity  in  the  vertical  flues  may  be  from  600  to  700  feet  per 
minute,  although  the  lower  velocity  is  preferable. 

The  size  of  the  inlet  registers  should  be  such  that  the  velocity 
of  the  entering  air  will  not  exceed  350  to  400  feet  per  minute. 

When  the  air  is  delivered  through  a  register  at  the  high  velocities 
mentioned,  some  means  must  be  provided  for  diffusing  the  entering 
current,  in  order  to  prevent  disagreeable  draughts.  This  is  usually 
accomplished  by  the  use  of  deflecting  blades  of  galvanized  iron,  set 
in  a  vertical  position  and  at  varying  angles,  so  that  the  air  is  thrown 
towards  each  side  as  it  issues  from  the  register.  The  size  of  the 
vent  flues  should  be  about  the  same  as  for  a  gravity  system — that  is, 
about  6  square  feet  for  a  standard  classroom,  and  in  the  same  pro- 
portion for  smaller  rooms. 

Vent-flue  heaters  are  not  usually  required  in  connection  with  a 
fan  system,  as  the  force  of  the  fan  is  sufficient  to  supply  the  required 


HEATING  AND  VENTILATION 


201 


Sri 

!? 


202  HEATING  AND  VENTILATION 

quantity  of  air  at  all  times  without  the  aspirating  effect  of  the  vent 
flues. 

The  method  of  piping  shown  in  Fig.  173  applies  especially  to 
buildings  of  large  size.  In  the  case  of  medium-sized  buildings,  it 
is  often  possible  to  use  pin  radiation  for  the  main  heater,  placing  the 
same  well  above  the  water-line  of  the  boilers  and  thus  returning  the 
condensation  by  gravity,  without  the  use  of  pumps  or  traps.  When 
this  arrangement  is  used,  an  engine  with  a  large  cylinder  should  be 
employed,  so  that  the  steam  pressure  will  not  exceed  15  or  18  pounds, 
and  the  whole  system,  including  the  direct  surface,  may  be  run  upon 
the  same  system. 

This  is  a  very  simple  arrangement,  and  is  adapted  to  all  build- 
ings of  small  and  medium  size  where  the  heater  can  be  placed  at  a 
sufficient  height  above  the  boilers. 

Temperature  control  is  usually  secured  automatically  by  placing 
pneumatic  valves  upon  either  the  direct  or  supplementary  heaters. 
Mixing  dampers  are  sometimes  used  instead,  in  the  latter  case.  Every 
fan  system  should  be  provided  with  a  thermometer  of  large  size  for 
indicating  the  temperature  of  the  air  in  the  main  duct  just  beyond 
the  fan. 

The  ventilation  of  the  toilet-rooms  of  a  school  building  is  a 
matter  of  the  greatest  importance.  The  first  requirement  is  that  the 
air-movement  shall  be  into  these  rooms  from  the  corridors  instead  of 
outward.  To  obtain  this  result,  it  is  necessary  to  produce  a  slight 
vacuum  within,  and  this  cannot  well  be  done  if  fresh  air  is  forced 
into  them. 

One  of  the  most  satisfactory  arrangements  is  to  provide  exhaust 
ventilation  only,  and  to  remove  the  greater  part  of  the  air  through 
local  vents  connecting  with  the  fixtures. 

Hospitals.  The  best  system  for  heating  and  ventilating  a  hos- 
pital depends  upon  the  character  and  arrangement  of  the  buildings. 
It  is  desirable  in  all  cases  to  do  the  heating  from  a  central  plant, 
rather  than  to  carry  fires  in  the  separate  buildings,  both  on  account 
of  economy  and  for  cleanliness. 

In  the  case  of  small  cottage  hospitals  with  two  or  three  buildings 
placed  close  together,  indirect  hot  water  affords  a  desirable  system  for 
the  wards,  with  direct  heat  for  the  other  rooms;  but  where  there  are 
several  buildings,  and  especially  if  they  are  some  distance  apart,  it 


HEATING  AND  VENTILATION  203 

becomes  necessary  to  substitute  steam  unless  the  water  is  pumped 
through  the  mains.  For  large  city  buildings,  a  fan  system  is  always 
desirable. 

If  the  building  is  tall  compared  with  its  ground  area,  so  that 
the  horizontal  supply*  ducts  will  be  comparatively  short,  the  double- 
duct  system  may  be  used  with  good  results.  Where  the  rooms  are 
of  good  size,  and  the  number  of  supply  flues  not  great,  the  use  of 
supplementary  heaters  at  the  bases  of  the  flues  makes  a  satisfactory 
arrangement.  Direct  radiation  should  never  be  used  in  the  wards 
when  it  can  be  avoided,  even  in  connection  with  an  independent  air- 
supply,  as  it  offers  too  great  an  opportunity  for  the  accumulation  of 
dust  in  places  which  are  difficult  to  reach. 

It  is  common  to  provide  from  80  to  100  cubic  feet  of  air  per 
minute  per  patient  in  ordinary  wards,  and  from  100  to  120  cubic  feet 
in  contagious  wards. 

The  usual  ward  building  of  a  modern  cottage-hospital  generally 
contains  a  main  ward  having  from  8  to  12  beds,  and  a  number  of 
private  rooms  of  one  bed  each. 

In  addition  to  these,  there  are.  a  diet  kitchen,  duty-room,  toilet- 
rooms,  bathrooms,  linen-closets,  and  lockers. 

For  moderately  sheltered  locations,  30  square  feet  of  indirect 
steam  radiation  has  been  found  sufficient  in  zero  weather  for  a  single 
ward  with  one  exposed  wall  and  a  single  window,  when  upon  the 
south  side  of  the  building. 

For  northerly  rooms,  40  square  feet  should  be  used.  In  exposed 
locations,  the  heaters  may  be  made  40  and  50  square  feet  for  north 
and  south  rooms  respectively.  The  standard  pin-radiators  rated  at 
10  square  feet  of  heating  surface  per  section,  are  commonly  used  for 
this  purpose.  In  case  hot  water  is  used,  the  same  number  of  sections 
of  the  deep-pin  pattern  rated  at  15  square  feet  each  may  be  employed, 
making  a  total  of  45  and  60  square  feet  per  room.  For  corner  rooms 
having  two  exposed  walls  and  two  windows,  the  amount  of  radiation 
should  be  increased  about  50  per  cent  over  that  given  above. 

The  wards  are  usually  furnished  with  fireplaces  which  provide 
for  the  discharge  ventilation.  In  case  the  fireplaces  are  omitted,  a 
special  vent  flue,  either  of  brick  or  of  galvanized  iron,  should  be  pro- 
vided. These  should  not  be  less  than  8  by  12  inches  for  single  wards, 
and  the  equivalent  for  each  bed  in  a  large  ward.  Each  flue  of  this 


204  HEATING  AND  VENTILATION 

kind  should  have  a  loop  of  steam  pipe  for  producing  a  draught.  A 
loop  of  1-inch  pipe,  10  or  12  feet  in  height,  is  usually  sufficient  for 
this  purpose. 

Other  rooms  than  wards  are  usually  heated  with  direct  radia- 
tors, the  sizes  of  which  may  be  computed  in  the  same  manner  as  for 
dwelling-houses. 

.  Steam  tables  for  the  kitchen,  sterilizers,  and  laundry  machinery, 
require  higher  pressures  than  is  necessary  for  heating. 

In  large  plants  the  boilers  are  usually  run  at  high  pressure,  and 
the  pressure  reduced  for  heating.  A  good  arrangement  for  small 
plants  is  to  provide  sufficient  boiler  power  for  warming  and  ventilating 
purposes,  and  run  at  a  pressure  of  3  to  5  pounds.  In  addition  to 
this,  a  small  high-pressure  boiler  carrying  70  or  80  pounds  should  be 
furnished  for  laundry  work  and  water  heating. 

Churches.  Churches  may  be  warmed  by  furnaces,  by  indirect 
steam,  or  by  means  of  a  fan.  For  small  buildings  the  furnace  is 
more  commonly  used.  This  apparatus  is  the  simplest  of  all  and  is 
comparatively  inexpensive.  Heat  may  be  generated  quickly,  and 
when  the  fires  are  no  longer  needed,  they  may  be  allowed  to  go  out 
without  danger  of  damage  to  any  part  of  the  system  from  freezing. 

It  is  not  usually  necessary  that  the  heating  apparatus  be  large 
enough  to  warm  the  entire  building  at  one  time  to  70  degrees  with 
frequent  change  of  air.  If  the  building  is  thoroughly  warmed  before 
occupancy,  either  by  rotation  or  by  a  slow  inward  movement  of 
outside  air,  the  chapel  or  Sunday-school  room  may  be  shut  off  until 
near  the  close  of  the  service  in  the  auditorium,  when  a  portion  of  the 
warm  air  may  be  turned  into  it.  When  the  service  ends,  the  switch- 
damper  is  opened  wide,  and  all  the  air  is  discharged  into  the  Sunday- 
school  room.  The  position  of  the  warm-air  registers  will  depend 
somewhat  upon  the  construction  of  the  building,  but  it  is  well  to  keep 
them  near  the  outer  walls  and  the  colder  parts  of  the  room.  Large 
inlet  registers  should  be  placed  in  the  floor  near  the  entrance  .doors, 
to  stop  cold  draughts  from  blowing  up  the  aisles  when  the  doors  are 
opened,  and  also  to  be  used  as  foot-warmers. 

Ceiling  ventilators  are  generally  provided,  but  should  be  no 
larger  than  is  necessary  to  remove  the  products  of  combustion  from 
the  gaslights,  etc.  If  too  large,  much  of  the  warmest  and  purest 
air  will  escape  through  them.  The  main  vent  flues  should  be  placed 


HEATING  AND  VENTILATION  205 

in  or  near  the  floor  and  should  be  connected  with  a  vent  shaft  leading 
outboard.  This  flue  should  be  provided  with  a  small  stove  or  flue 
heater  made  specially  for  this  purpose.  In  cold  weather  the  natural 
draught  will  be  found  sufficient  in  most  cases. 

The  same  general  rules  are  to  be  followed  in  the  case  of 
indirect  steam  as  have  been  described  for  furnace  heating.  The 
stacks  are  placed  beneath  the  registers  or  flues,  and  mixing  dampers 
provided.  If  there  are  large  windows,  flues  should  be  arranged  to 
open  in  the  window-sills,  so  that  a  sheet  of  warm  air  may  be  delivered 
in  front  of  the  windows,  to  counteract  the  effects  of  cold  down-draughts 
from  the  exposed  glass.  These  flues  may  usually  be  made  3  or  4 
inches  in  depth,  and  should  extend  the  entire  width  of  the  window. 
Small  rooms,  such  as  vestibules,  library,  pastor's  room,  etc.,  are  usually 
heated  with  direct  radiators.  Rooms  which  are  used  during  the 
week  are  often  connected  with  an  independent  heater  so  that  they 
may  be  warmed  without  running  the  large  boilers,  as  would  otherwise 
be  necessary. 

When  a  fan  is  used,  it  is  desirable,  if  possible,  to  deliver  the  air 
to  the  auditorium  through  a  large  number  of  small  openings.  This 
is  often  done  by  constructing  a  shallow  box  under  each  pew,  running 
its  entire  length,  and  connecting  it  with  the  distributing  ducts  or  a 
plenum  space  by  means  of  a  pipe  from  below.  The  air  is  delivered 
at  a  low  velocity  through  a  long  slot,  as  shown  in  Fig.  174. 

The  warm-air  flues  in  the  window-sills  should  be  retained,  but 
may  be  made  shallower,  and  the  air  forced  in  at  a  high  velocity. 

If  the  auditorium  has  a  sloping  floor,  a  plenum  space  may  be 
provided  between  the  upper  or  raised  portion  and  the  main  floor. 
Sometimes  a  shallow  basement  3  or  4  feet  in  height,  with  a  cemented 
floor,  and  extending  under  the  entire  auditorium,  is  used  as  an  air 
or  plenum  space. 

If  the  basement  is  of  good  height  and  used  for  storage  or  other 
purposes,  it  is  necessary  to  carry  galvanized-iron  ducts  at  the  ceiling 
under  the  center  of  each  double  row  of  pews,  and  to  connect  with 
each  pair  by  means  of  branch  uptakes.  The  size  of  these  should 
be  equal  to  3  or  4  square  inches  for  each  occupant. 

Another  method  is  to  supply  the  air  through  a  small  register  in 
the  end  of  each  pew.  This  simplifies  the  pew  construction  some^ 
what,  but  otherwise  is  not  so  satisfactory  as  the  preceding  method. 


206 


HEATING  AND  VENTILATION 


If  the  special  pew  construction  is  too  expensive,  or  for  any  other 
reason  cannot  well  be  used,  and  the  fan  is  to  be  retained,  the  greater 
part  of  the  air  is  best  introduced  through  wall  registers  placed  about 
8  feet  above  the  floor,  with  exhaust  openings  at  or  near  the  floor. 
By  this  arrangement  the  air  is  thrown  horizontally  toward  the  center 
of  the  church,  and  much  of  it  falls  to  the  breathing  level  without 
rising  to  the  upper  part  of  the  room. 

Halls.  The  treatment  of  a  large  audience  hall  is  similar  to  that 
of  a  church,  the  warming  being  usually  done  in  one  of  the  three  ways 
already  described.  Where  a  fan  is  used,  the  air  is  commonly  delivered 

through  wall  registers  placed  in 
part  near  the  floor,  and  partly  at  a 
height  of  7  or  8  feet  above  it.  They 
should  be  made  of  ample  size, 
so  that  there  will  be  freedom  from 
draughts.  A  part  of  the  vents 
should  be  placed  in  the  ceiling, 
and  the  remainder  near  the  floor. 
All  ceiling  vents,  in  both  halls  and 
churches,  should  be  provided  with 
dampers  having  means  for  hold- 
ing them  in  any  desired  position. 
If  indirect  gravity  heaters  are 
used,  it  will  generally  be  necessary 
to  place  heating  coils  in  the  vent 
flues  for  use  in  mild  weather;  but 
if  the  fresh  air  is  supplied  by 
means  of  a  fan,  there  will  usually  be 

pressure  enough  in  the  room  to  force  the  air  out  without  the  aid  of 
other  means.  When  the  vent  air-ways  are  restricted,  or  the  air  is 
impeded  in  any  way,  electric  ventilating  fans  are  often  used.  These 
give  especially  good  results  in  warmer  weather,  when  natural  venti- 
lation is  sluggish.  The  temperature  may  be  regulated  either  by 
using  the  double-duct  system  or  by  shutting  off  or  turning  on  a  greater 
or  less  number  of  sections  in  the  main  heater.  After  an  audience 
hall  is  once  warmed  and  filled  with  people,  very  little  heat  is  required 
to  keep  it  comfortable,  even  in  the  coldest  weather. 

Theaters.     IP    designing   heating   and   ventilating   systems   for 


Fig.  174.    An  Approved  Method  of  De- 
livering Warm  Air  to  the  Audi- 
torium of  a  Church. 


HEATING  AND  VENTILATION  207 

theaters,  a  wide  experience  and  the  greatest  care  are  necessary  to 
secure  the  best  results.  A  theater  consists  of  three  parts:  the  body 
of  the  house,  or  auditorium;  the  stage  and  dressing-rooms,  and  the 
foyer,  lobbies,  corridors,  stairways,  and  offices.  Theaters  are  usually 
located  in  cities,  and  surrounded  with  other  buildings  on  two  or  more 
sides,  thus  allowing  no  direct  connection  by  windows  with  the  ex- 
ternal air;  for  this  reason  artificial  means  are  necessary  for  providing 
suitable  ventilation,  and  a  forced  circulation  by  means  of  a  fan  is  the 
only  satisfactory  means  of  accomplishing  this.  It  is  usually  advisable 
to  create  a  slight  excess  of  pressure  in  the  auditorium,  in  order  that 
all  openings  shall  allow  for  the  discharge  rather  than  the  inward 
leakage  of  air. 

The  general  and  most  approved  method  of  air-distribution  is 
to  force  it  into  closed  spaces  beneath  the  auditorium  and  balcony 
floors,  and  allow  it  to  discharge  upward  through  small  openings 
among  the  seats.  One  of  the  best  methods  is  through  chair-legs 
of  special  latticed  design,  which  are  placed  over  suitable  openings  in 
the  floor;  in  this  way  the  air  is  delivered  to  the  room  in  small  streams, 
at  a  low  velocity,  without  draughts  or  currents.  The  discharge 
ventilation  should  be  largely  through  ceiling  vents,  and  this  may  be 
assisted  if  necessary  by  the  use  of  ventilating  fans.  \7ent  openings 
should  also  be  provided  at  the  rear  of  the  balconies,  either  in  the  wall 
or  in  the  ceiling,  and  these  should  be  connected  with  an  exhaust  fan 
either  in  the  basement  or  in  the  attic,  as  is  most  convenient. 

The  close  seating  of  the  occupants  produces  a  large  amount  of 
animal  heat,  which  usually  increases  the  temperature  from  6  to  10 
degrees,  or  even  more;  so  that,  in  considering  a  theater  once  filled 
and  thoroughly  warmed,  it  becomes  more  of  a  question  of  cooling 
than  one  of  warming  to  produce  comfort. 

The  dressing-rooms  should  be  provided  with  a  generous  supply 
of  fresh  air,  sufficient  to  change  the  entire  contents  once  in  10  minutes 
at  least,  and  should  have  discharge  flues  of  sufficient  size  to  carry 
away  this  amount  of  air  at  a  velocity  not  exceeding  300  feet  per 
minute,  unless  connected  with  an  exhaust  fan,  in  which  case  the 
velocity  may  be  doubled.  The  foyer,  corridors,  dressing-rooms, 
etc.,  are  generally  heated  by  direct  radiators,  which  may  be  con- 
cealed by  ornamental  screens  if  desired. 

Office  Buildings.    This  class  of  buildings  may  be  satisfactorily 


208  HEATING  AND  VENTILATION 

warmed  by  direct  steam,  hot  water,  or,  where  ventilation  is  desired, 
by  the  fan  system.  Probably  direct  steam  is  used  more  frequently 
than  any  other  system  for  this  purpose.  Vacuum  systems  are  well 
adapted  to  the  conditions  usually  found  in  this  type  of  building, 
as  most  modern  office  buildings  have  their  own  light  and  power 
plants,  and  the  exhaust  steam  can  thus  be  utilized  for  heating  pur- 
poses. The  piping  may  be  either  single  or  double.  If  the  former 
is  used,  it  is  better  to  carry  a  single  main  riser  to  the  upper  story,  and 
run  drops  to  the  basement,  as  by  this  means  the  steam  and  water 
flow  in  the  same  direction,  and  much  smaller  pipes  can  be  used  than 
would  be  the  case  if  risers  were  carried  from  the  basement  upward. 

Special  provision  must  be  made  for  the  expansion  of  the  risers  or 
drops  in  tall  buildings.  They  are  usually  anchored  at  the  center, 
and  allowed  to  expand  in  both  directions.  The  connections  with  the 
radiators  must  not  be  so  rigid  as  to  cause  undue  strains  or  to  lift  the 
radiators  from  the  floor. 

It  is  customary,  in  most  cases,  to  make  the  connections  with 
the  end  farthest  from  the  riser;  this  gives  a  length  of  horizontal  pipe 
which  has  a  certain  amount  of  spring,  and  will  care  for  any  vertical 
movement  of  the  riser  that  is  likely  to  occur.  Forced  hot-water 
circulation  is  often  used  in  connection  writh  exhaust  steam.  The 
water  is  warmed  by  the  steam  in  large  heaters  similar  to  feed-water 
heaters  and  is  circulated  through  the  system  by  means  of  centrifugal 
pumps.  This  has  the  usual  advantage  of  hot  water  over  steam, 
inasmuch  as  the  temperature  of  the  radiators  may  be  regulated  to 
suit  the  conditions  of  outside  temperature. 

When  a  fan  system  is  used  the  arrangement  of  the  air-ways  is 
usually  somewhat  different  from  any  of  those  yet  described.  Owing 
to  the  great  height  of  these  buildings,  and  the  large  number  of  small 
rooms  which  they  contain,  it  is  impossible  to  carry  up  separate  flues 
from  the  basement.  One  of  the  best  arrangements  is  to  construct 
false  ceilings  in  the  corridor-ways  on  each  floor,  thus  forming  air- 
ducts  which  .may  receive  their  supply  through  one  or  more  large  up- 
takes extending  from  the  basement  to  the  top  of  the  building.  These 
corridor  air-ways  may  be  tapped  over  the  door  of  each  room,  the 
openings  being  provided  with  suitable  regulating  dampers  for  gauging 
the  air-supply  to  each.  Adjustable  deflectors  should  be  placed  in 
the  main  air-shafts  for  proportioning  the  quantity  to  be  delivered 


HEATING  AND  VENTILATION  209 

to  each  floor.  If  both  supply  and  discharge  ventilation  are  to  be 
provided,  the  fresh  air  may  be  carried  in  galvanized-iron  ducts  within 
the  ceiling  spaces,  and  the  remainder  used  for  conveying  the  exhausted 
air  to  uptakes  leading^  to  a  discharge  fan  placed  upon  the  roof  of 
the  building.  In  both  of  these  cases,  it  is  assumed  that  heat  is  sup- 
plied to  the  rooms  by  direct  radiation,  and  that  the  air-supply  is  for 
ventilation  only. 

Apartment  Houses.  These  are  warmed  by  furnaces,  direct 
steam,  and  hot  water.  Furnaces  are  more  often  used  in  the  smaller 
houses,  as  they  are  cheaper  to  install,  and  require  a  less  skilful  at- 
tendant to  operate  them.  Steam  is  probably  used  more  than  any 
other  system  in  blocks  of  larger  size.  A  well-designed  single-pipe 
connection,  with  automatic  air-valves  dripped  to  the  basement,  is 
probably  the  most  satisfactory  in  this  class  of  work.  People  who 
are  more  or  less  unfamiliar  with  steam  systems  are  apt  to  overlook 
one  of  the  valves  in  shutting  off  or  turning  on  steam;  and  where  only 
one  valve  is  used,  the  difficulty  arising  from  this  is  avoided.  Where 
pet-cock  air-valves  are  used,  they  are  often  left  open  through  careless- 
ness ;  and  the  automatic  valves,  unless  'dripped,  are  likely  to  give  more 
or  less  trouble. 

Greenhouses  and  Conservatories.  Buildings  of  this  class  are 
heated  in  some  cases  by  steam  and  in  others  by  hot  water,  some  florists 
preferring  one  and  some  the  other.  Either  system,  when  properly 
designed  and  constructed,  should  give  satisfaction,  although  hot 
water  has  its  usual  advantage  of  a  variable  temperature.  The 
methods  of  piping  are,  in  a  general  way,  like  those  already  described, 
and  the  pipes  may  be  located  to  run  underneath  the  beds  of  growing 
plants  or  above,  as  bottom  or  top  heat  is  desired.  The  main  is  gen- 
erally run  near  the  upper  part  of  the  greenhouse  and  to  the  farthest 
extremity,  in  one  or  more  branches,  with  a  pitch  upward  from  the 
heater  for  hot  water  and  with  a  pitch  downward  for  steam.  The 
principal  radiating  surface  is  made  of  parallel  lines  of  1J  inch  or 
larger  pipe,  placed  under  the  benches  and  supplied  by  the  return 
current.  Figs.  175,  176,  and  177  show  a  common  method  of  running 
the  piping  in  greenhouse  work.  Fig.  175  shows  a  plan  and  eleva- 
tion of  the  building  with  its  lines  of  pipe;  and  Figs.  176  and  177  give 
details  of  the  pipe  connections  of  the  outer  and  inner  groups  of  pipes 
respectively. 


210 


HEATING  AND  VENTILATION 


Any  system  of  piping  which  gives  free  circulation  and  which  is 
adapted  to  the  local  conditions,  should  give  satisfactory  results.  The 
radiating  surface  may  be  computed  from  the  rules  already  given. 
As  the  average  greenhouse  is  composed  almost  entirely  of  glass,  we 


Fig.  175.    Plan  and  Elevation  Showing  One  Method  of  Running  Piping  in  a  Greenhouse 

may  for  purposes  of  calculation  consider  it  such;  and  if  we  divide 
the  total  exposed  surface  by  4,  we  shall  get  practically  the  same 
result  as  if  we  assumed  a  heat  loss  of  85  B.  T.  U.  per  square  foot  of 
surface  per  hour,  and  an  efficiency  of  330  B.  T.  U.  for  the  heating 


HEATING  AND  VENTILATION  211 

coils;  so  that  we  may  say,  in  general,  that  the  square  feet  of  radiating 
surface  required  equals  the  total  exposed  surface,  divided  by  4  for 
steam  coils,  and  by  2.5  for  hot-water.  These  results  should  be  in- 
creased from  10  to  20  per  cent  for  exposed  locations. 

CARE  AND  MANAGEMENT 

The  care  of  furnaces,  hot-water  heaters,  and  steam  boilers  has 
been  discussed  in  connection  with  the  design  of  these  different  systems 
of  heating,  and  need  not  be  repeated.  The  management  of  the 
heating  and  ventilating  systems  in  large  school  buildings  is  a  matter 
of  much  importance,  especially  in  those  using  a  fan  system.  To  obtain 
the  best  results,  as  much  depends  upon  the  skill  of  the  operating 
engineer  as  upon  that  of  the  designer. 

Beginning  in  the  boiler-room,  he  should  exercise  special  care 
in  the  management  of  his  fires,  and  the  instruction  given  in  "Boiler 
Accessories"  should  be  carefully  followed;  all  flues  and  smoke 
passages  should  be  kept  clear  and  free  from  accumulations  of  soot 
and  ashes  by  means  of  a  brush  or  steam  jet.  Pumps  and  engine  should 
be  kept  clean  and  in  perfect  adjustment,  and  extra  care  should  be 
taken  when  they  are  in  rooms  through  which  the  air-supply  is  drawn, 
or  the  odor  of  oil  will  be  carried  to  the  rooms.  All  steam  traps  should 
be  examined  at  regular  intervals  to  see  that  they  are  in  working  order; 
and  upon  any  sign  of  trouble,  they  should  be  taken  apart  and  care- 
fully cleaned. 

The  air-valves  on  all  direct  and  indirect  radiators  should  be 
inspected  often;  and  upon  the  failure  of  any  room  to  heat  properly, 
the  air-valve  should  first  be  looked  to  as  a  probable  cause  of  the  diffi- 
culty. Adjusting  dampers  should  be  placed  in  the  base  of  each  flue, 
so  that  the  flow  to  each  room  may  be  regulated  independently.  In 
starting  up  a  new  plant,  the  system  should  be  put  in  proper  balance 
by  a  suitable  adjustment  of  these  dampers;  and,  when  once  adjusted, 
they  should  be  marked,  and  left  in  these  positions.  The  temperature 
of  the  rooms  should  never  be  regulated  by  closing  the  inlet  registers. 
These  should  never  be  touched  unless  the  room  is  to  be  unused  for 
a  day  or  more. 

In  designing  a  fan  system,  provision  should  be  made  Tor  air- 
rotation',  that  is,  the  arrangement  should  be  such  that  the  same 
air  may  be  taken  from  the  building  and  passed  through  the  fan  and 


212 


HEATING  AND  VENTILATION 


Fig.  176.    Connections  of  Outer  Groups  of  Pipes  of  Greenhouse  Shown  in  Fig.  175. 


Fig.  177.    Connections  of  Inner  Groups  of  Pipes  of  Greenhouse  Shown  in  Fig.  175, 


HEATING  AND  VENTILATION  213 

heater  continuously.  This  is  usually  accomplished  by  closing  the 
main  vent  flues  and  the  cold-air  inlet  to  the  building,  then  opening  the 
class-room  doors  into  the  corridor-ways,  and  drawing  the  air  down 
the  stair-wells  to  the  basement  and  into  the  space  back  of  the  main 
heater  through  doors^provided  for  this  purpose.  In  warming  up  a 
building  in  the  morning,  this  should  always  be  done  until  about 
fifteen  minutes  before  school  opens.  The  vent  flues  should  then  be 
opened,  doors  into  corridors  closed,  cold-air  inlets  opened  wide,  and 
the  full  volume  of  fresh  air  taken  from  out  of  doors. 

At  night  time  the  dampers  in  the  main  vents  should  be  closed, 
to  prevent  the  warm  air  contained  in  the  building  from  escaping. 
The  fresh  air  should  be  delivered  to  the  rooms  at  a  temperature  of 
from  70  to  75  degrees;  and  this  temperature  must  be  obtained  by 
proper  use  of  the  shut-off  valves,  thus  running  a  greater  or  less  number 
of  sections  on  the  main  heater.  A  little  experience  will  show  the 
engineer  how  many  sections  to  carry  for  different  degrees  of  outside 
temperature.  A  dial  thermometer  should  be  placed  in  the  main 
warm-air  duct  near  the  fan,  so  that  the  temperature  of  the  air  delivered 
to  the  rooms  can  be  easily  noted. 

The  exhaust  steam  from  the  engine  and  pumps  should  be  turned 
into  the  main  heater;  this  will  supply  a  greater  number  of  sections 
in  mild  weather  than  in  cold,  owing  to  the  less  rapid  con- 
densation. 


INDEX 


A  Page 
Air 

analysis  of 8 

force  for  moving 11 

measurement  of  velocity  of 11 

required  for  ventilation 9 

Air-compressor 189 

Air  distribution 12 

Air-filters  and  air-washers 194 

Air-valves 58,  109 

Air- venting 105 

Atmosphere,  composition  of 7 

Automatic  return-pumps 130 

B 

Balance  pipe 131 

Back-pressure  valve 128 

Blow-off  tank 68 

Boiler  horse-power 36 

British  thermal  unit 13 

C 

Centrifugal  fan 160 

theory  of 163 

Centrifugal  pumps 120 

Chimney  flues 28 

Circulation  coils 45 

Cold-air  ducts 82 

Composition  of  atmosphere 7 

carbonic  acid  gas 7 

nitrogen * 7 

oxygen 7 

D 

Damper-regulators •  134 

Dampers 77, 192 

Diaphragm  motors 

Direct  hot-water  heating 4,    97 

air- venting 105 

circulation  systems 

combination  systems 107 

expansion  tank 103 


216  INDEX 


Direct  hot-water  heating  Page 

fittings 110 

overhead  distribution 103 

pipe  connections 105 

piping  systems 101 

radiating  surface,  types  of 99 

radiators,  efficiency  of • .  .  .  .  100 

valves 109 

Direct-indirect  radiators 4 

Direct-steam  heating 2,  42 

blow-off  tank 68 

boiler  connections 67 

cast-iron  radiators 43 

circulation  coils 45 

pipe  radiators 45 

pipe  sizes 60 

pipes,  expansion  of •.  .  56 

piping  systems 49 

one-pipe  circuit 54 

one-pipe  relief 52 

two-pipe 49 

radiators 

connections  of 55 

efficiency  of ' 47 

location  of 49 

returns 66 

valves 58 

Disc  or  propeller  fans 171 

capacity  of 172 

E 

Efficiency  of 

heaters 74 

pipe  heaters 152 

radiators 47,  100 

Electric  heat  and  energy 186 

Electric  heaters 

calculation  of 187 

connections  for 187 

construction  of 186 

Electric  heating -6,  186 

cost  of 

heaters. .  v 187 

Electric  motors - 177 

Exhaust  head •  •  •  130 

Exhaust  method  of  forced  blast 147 

Exhaust-steam  heating ....  5,  124 

automatic  return-pumps 

back-pressure  valve 128 


INDEX  217 


Exhaust-steam  heating  Page 

damper-regulators 134 

exhaust  head 130 

grease  extractor ; , 127 

pipe  connections ,  135 

reducing  valves.  .^ .• 126 

return  traps 132 

Expansion  of  pipes 56 

Expansion  tank 103 

F 

Fan  engines 175 

Fans 159 

centrifugal 1 60 

disc  or  propeller 171 

electric  motors  for 177 

engines  for 1 75 

Firepot 23 

Forced  blast 147 

cast-iron  heaters,  efficiency  of , 157 

double-duct  system. 183 

ducts  and  flues,  area  of 178 

exhaust  method 147 

for  factory  heating 179 

fan*  engines . 1 75 

fans : 159 

heating  surface,  form  of 148 

pipe  heaters,  efficiency  of 152 

plenum  method 148 

Forced  blast  heating 6 

Forced  hot-water  circulation 117 

heaters 

mains  and  branches,  sizes  of 118 

piping  systems 117 

pumps 

Furnace  heating •  •  •  19 

chimney  flues 28 

cold-air  box 28 

combination  systems 

combustion  chamber 

efficiency 

firepots 

furnaces 

care  and  management 34 

location  of 27 

types  of 

grates 

heating  capacity 

heating  surface 2^ 


218  INDEX 


Furnace  heating  Page 

radiator 24 

registers 33 

return  duct 29 

smoke-pipes 27 

warm-air  pipes 30 

Furnaces 1 

care  and  management  of , 34 

types  of 20 

G 

Gate- valves 109 

Globe  valve 58 

Grates 22 

Grease  extractor 127 

H 

Heat  loss  from  buildings 13 

by  air-leakage 14 

by  ventilation 18 

per  walls  and  windows 13 

Heating  and  ventilation  of 

apartment  houses 209 

churches 204 

greenhouses  and  conservatories 209 

halls .* 206 

hospitals 202 

office  buildings 207 

school  buildings , 196 

theaters ^ 206 

Heating  and  ventilation  systems,  care  and  management  of 211 

Horse-power  for  ventilation 42 

Hot- water  heaters 94 

care  and  management  of 116 

Humidostat 193 

I 

Indirect  hot-water  heating 5,  1 13 

flues  and  casings 115 

pipe  connections 115 

pipe  sizes 116 

radiators,  types  of 114 

stacks,  size  of 114 

Indirect  steam  heating 3,  71 

cold-air  ducts 82 

dampers 77 

direct-indirect  radiators 91 

heaters 

efficiency  of 74 

types  of 72 


INDEX  219 


Indirect  steam  heating  Page 

pipe  connections « 89 

pipe  sizes 90 

registers 87 

stacks  and  casings 77 

vent  flues f. 83 

warm-air  flues 81 

P 

Paul  vacuum  heating  system 145 

Plenum  method  of  forced  blast 148 

R 

Radiators,  efficiency  of 47 

Reducing  valves 126 

Registers 33 

Return  traps 132 

S 

Sectional  boilers 39 

Stacks  and  casings , 77 

Steam  boilers 36 

sectional „ 39 

tubular 36 

Steam-heating  boilers,  care  and  management  of 92 

Stoves 1 

T 

Tables 

boiler,  size  of,  for  different  conditions 38 

air,  number  of  changes  in,  required  in  various  rooms 11 

air,  power  required  for  moving  under  different  pressures 170 

air,  quantity  of,  required  per  person 10 

air  required  for  ventilation  of  various  classes  of  buildings 10 

air-flow  per  flues  of  various  heights  under  varying  conditions  of  tem- 
perature    86 

direct  radiating  surface  supplied  by  mains  of  different  sizes  and 

lengths  of  run Ill 

disc  fans,  capacity,  speed,  etc 175 

efficiency  of  radiators,  coils,  etc 47 

fan  speeds,  pressures,  and  velocities  of  air-flow 165 

fans,  effective  area  of 167 

firepot  dimensions 27 

flow  of  steam  in  pipes  of  other  lengths  than  100  ft.,  factors  for  calcu- 
lating   62 

flow  of  steam  in  pipes  under  initial  pressures  above  5  Ibs.,  factors 

for  calculating 61 

flow  of  steam  in  pipes  of  various  sizes,  etc 61 

grate  area  per  H.  P.  forMifferent  rates  of  evaporation  and  combustion  37 

heat  loss,  factor  for  calculating,  for  other  than  southern  exposures  15 


220  INDEX 


Tables  Page 
heat  losses  in  B.  T.  V.  per  sq.  ft.  of  surface  per  hour,  southern  ex- 
posure   14 

heaters,  forced  blast,  dimensions  of 155 

heating  surface  supplied  by  pipes  of  various  sizes 64 

heating  systems,  relative  cost  of :  .  .  .  4 

indirect  radiating  surface  supplied  by  pipes  of  various  sizes.  . 91 

mains,  sizes  of  for  different  conditions 121 

oval  pipe  dimensions 32 

pipe  heater  data 154 

pipe  sizes 159 

pipe  sizes  from  boiler  to  main  header 07 

pipe  sizes  for  radiator  connections G6 

radiating  ^surface  on  different   floors  supplied  by  pipes  of  different 

sizes Ill 

radiating  surface  supplied  by  pipes  of  various  sizes,  indirect  hot-water 

system 116 

radiating  surface  supplied  by  steam  risers 65 

registers,  sizes  of  for  different  sizes  of  pipes 33 

return,  blow-off,  and  feed  pipes,  sizes  of 68 

steam  pipes,  sizes  of  returns  for 66 

warm-air  pipe  dimensions 30 

Telethermometer 193 

Temperature  regulators 189 

air-compressor 189 

dampers 192 

diaphragm  motors 192 

diaphragm  valve 191 

humidostat 193 

telethermometer. ...  193 

thermostat 190 

Thermostat .  .142,  190 

Tubular  boilers 36 

V 

Vacuum  heating  systems 141 

Paul : 145 

Webster HI 

Vacuum  valve *>0 

Valves 58 

Vent  flues 

Ventilation 

air  required  .for 

horse-power  for 

principles  of 7 

W 

Warm-air  flues 

Warming,  systems  of • 


INDEX  221 


Warming,  systems  of  Page 

direct  hot  water 4 

direct-indirect  radiators 4 

direct  steam 

electric  heating. . . ., : 6 

exhaust  steam !*. 5 

forced  blast 6 

furnaces 1 

indirect  hot  water 5 

indirect  steam 3 

stoves 1 

Water-seal  motor 142 

Water-tube  boilers 39 

Webster  vacuum  heating  system 141 


PEC    1 


f 


I  79734 


-.-.*• 


